Toner set for electrostatic charge image development, electrostatic charge image developer set, toner cartridge set, process cartridge, image forming apparatus, and image forming method

Abstract

To provide a toner set for electrostatic charge image development that exhibits high color developability of an image having a colored image on a white image, and prevents peeling-off of an image when it is folded.SOLUTION: A toner set for electrostatic charge image development has a white toner having white toner particles including polyester resin and a white coloring agent, and a colored toner other than white having colored toner particles including vinyl resin, polyester resin, and a colored coloring agent. In the colored toner particle, the mass ratio C of the polyester resin to the vinyl resin is 0.7 or more and 10 or less. When a cross section of the white toner particle is observed, the area ratio of the white coloring agent is 10% or more and 50% or less, and the number average particle diameter of the white coloring agent is 0.23 μm or more and 0.45 μm or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a toner set for developing an electrostatic image, an electrostatic image developer set, a toner cartridge set, a process cartridge, an image forming apparatus, and an image forming method. [Background technology]

[0002] 2. Description of the Related Art Conventionally, in electrophotographic image formation, it is known to use a white toner for the purpose of forming a colored image on a colored recording medium or a recording medium having transparency.

[0003] For example, Patent Document 1 proposes "an image forming method including an electrostatic latent image forming step of forming an electrostatic latent image on an electrostatic latent image carrier, a developing step of developing the electrostatic latent image using a toner including toner base particles containing a binder resin, a photoluminescent pigment, a white pigment, and a release agent to form a white toner image, a color toner image developing step of forming a color toner image using color toners, a transfer step of transferring the toner image to a recording medium, and a fixing step of fixing the transferred image transferred to the recording medium, wherein the white toner image is formed closer to the recording medium than the color toner images."

[0004] Furthermore, Patent Document 2 proposes "a toner set comprising at least one selected from a white toner including white toner particles containing white colored particles, a colored toner including colored toner particles containing colored particles, and a transparent toner including transparent toner particles, wherein the average circularity of the white toner particles is smaller than the average circularity of either the colored toner particles or the transparent toner particles, and the small diameter side number particle size distribution index of the white toner particles is larger than the small diameter side number particle size distribution index of either the colored toner particles or the transparent toner particles." [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-79868 A [Patent Document 2] JP 2018-97016 A Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the present invention is to provide a toner set for developing electrostatic images, which comprises a white toner having white toner particles containing a polyester resin and a white colorant, and a non-white color toner having colored toner particles containing a vinyl resin, a polyester resin, and a colored colorant, and which has higher color development of an image having a colored image on a white image and suppresses peeling of the image when folded, compared to a toner set for developing electrostatic images in which the mass ratio C of the polyester resin to the vinyl resin in the colored toner particles is less than 0.7 or exceeds 10, and in which, when a cross section of the colored toner particles is observed, the area ratio of the white colorant is less than 10% or exceeds 50%, or the number average particle size of the white colorant is less than 0.23 μm or exceeds 0.45 μm. [Means for solving the problem]

[0007] Means for solving the above problems include the following aspects. <1> a white toner having white toner particles including a polyester resin and a white colorant; a non-white color toner having color toner particles including a vinyl resin, a polyester resin, and a color colorant; having a mass ratio C of the polyester resin to the vinyl resin in the color toner particles is 0.7 or more and 10 or less; A toner set for developing electrostatic images, wherein, when a cross section of the white toner particle is observed, the area ratio of the white colorant is 10% or more and 50% or less, and the number average particle size of the white colorant is 0.23 μm or more and 0.45 μm or less. <2> In the color toner particles, a mass ratio C of the polyester resin to the vinyl resin is 2 or more and 6 or less. <1> 2. A toner set for developing electrostatic images according to claim 1 . <3> When a cross section of the white toner particle is observed, the area ratio of the white colorant is 20% or more and 50% or less, and the number average particle diameter of the white colorant is 0.23 μm or more and 0.30 μm or less. <1> or <2> 2. A toner set for developing electrostatic images according to claim 1 . <4> The white toner particles contain a vinyl resin. <1> ~ <3> 13. The toner set for developing electrostatic images according to claim 12. <5> a relationship between a mass ratio W of the polyester resin to the vinyl resin in the white toner particles and a mass ratio C of the polyester resin to the vinyl resin in the color toner particles satisfies −0.6≦WC≦5.6; <4> 2. A toner set for developing electrostatic images according to claim 1 . <6> a mass ratio W of the polyester resin to the vinyl resin in the white toner particles and a mass ratio C of the polyester resin to the vinyl resin in the color toner particles satisfy 0≦WC≦4; <5> 2. A toner set for developing electrostatic images according to claim 1 . <7> When a cross section of the white toner particle is observed, the ratio of white colorants having a particle size of 100 nm or less to the total white colorants is 30% by number or less. <1> ~ <6> 13. The toner set for developing electrostatic images according to claim 12. <8> When a cross section of the white toner particle is observed, the ratio of white colorants having a particle size of 100 nm or less to the total white colorants is 20% by number or less. <7> 2. A toner set for developing electrostatic images according to claim 1 . <9> <1> ~ <8> a white electrostatic image developer containing the white toner in the toner set for developing an electrostatic image according to any one of claims 1 to 5; <1> ~ <8> A color electrostatic image developer containing the color toner in the toner set for developing an electrostatic image according to any one of claims 1 to 5, an electrostatic image developer set comprising: <10> <1> ~ <8> a white toner cartridge that contains the white toner contained in the toner set for developing an electrostatic image according to any one of claims 1 to 4 and is detachably attached to an image forming apparatus; <1> ~ <8> a color toner cartridge that contains the color toner contained in the toner set for developing an electrostatic image according to any one of claims 1 to 4 and is detachably attached to an image forming apparatus; Toner cartridge set including: <11> <9> a first developing means containing the white electrostatic image developer contained in the electrostatic image developer set according to claim 1; <9> a second developing means containing the color electrostatic image developer contained in the electrostatic image developer set according to claim 1; Equipped with A process cartridge that is detachably attached to an image forming apparatus. <12> <9> a first image forming means for forming a white image using the white toner, the first image forming means including a first developing means containing the white electrostatic image developer included in the electrostatic image developer set described in <9> a second image forming means for forming a color image by using the color toner, the second image forming means including a second developing means containing the color electrostatic image developer included in the electrostatic image developer set described in a transfer means for transferring the white image and the color image onto a surface of a recording medium; a fixing means for fixing the white image and the color image transferred onto the surface of the recording medium; An image forming apparatus comprising: <13> <1> ~ <8> a first image forming step of forming a white image by the white toner contained in the toner set for developing an electrostatic image according to any one of the above items; <1> ~ <8> A second image forming step of forming a color image using the color toner contained in the toner set for developing an electrostatic image according to any one of the above items; a transfer step of transferring the white image and the color image onto a surface of a recording medium; a fixing step of fixing the white image and the color image transferred onto the surface of the recording medium; The image forming method according to claim 1, Effect of the Invention

[0008] <1> According to the invention, there is provided a toner set for developing electrostatic images, which comprises a white toner having white toner particles containing a polyester resin and a white colorant, and a colored toner other than white having colored toner particles containing a vinyl resin, a polyester resin, and a colored colorant, and which has a mass ratio C of the polyester resin to the vinyl resin in the colored toner particles that is less than 0.7 or exceeds 10, and when a cross section of the colored toner particles is observed, the area ratio of the white colorant is less than 10% or exceeds 50%, or the number average particle diameter of the white colorant is less than 0.23 μm or exceeds 0.45 μm, and which has higher color development of an image having a colored image on a white image and suppresses peeling of the image when folded, compared to a toner set for developing electrostatic images in which the mass ratio C of the polyester resin to the vinyl resin in the colored toner particles is less than 0.7 or exceeds 10, and peeling of the image when folded is suppressed.

[0009] <2> According to the invention, there is provided a toner set for developing electrostatic images, which has high color development for an image having a color image on a white image and suppresses peeling of the image when folded, compared to when the mass ratio C of the polyester resin to the vinyl resin in the color toner particles is less than 2 or exceeds 6. <3> According to the invention, there is provided a toner set for developing electrostatic images, which, when a cross section of a color toner particle is observed, has higher color development in an image having a color image on a white image and suppresses peeling of the image when folded, compared to a case in which the area ratio of the white colorant is less than 20% or more than 50%, or the number average particle size of the white colorant is less than 0.23 μm or more than 0.30 μm. <4> According to the invention, there is provided a toner set for developing electrostatic images, which has higher color development for an image having a colored image on a white image and suppresses peeling of the image when folded, compared to a case in which the white toner particles contain only a polyester resin as a binder resin. <5> According to the invention, there is provided a toner set for developing electrostatic images, which has higher color development for an image having a color image on a white image and suppresses peeling of the image when folded, compared to a case in which the relationship between the mass ratio W of the polyester resin to the vinyl resin in the white toner particles and the mass ratio C of the polyester resin to the vinyl resin in the color toner particles does not satisfy -0.6≦WC≦5.6. <6> According to the invention, there is provided a toner set for developing electrostatic images, which has higher color development for an image having a color image on a white image and suppresses peeling of the image when folded, compared to a case in which the relationship between the mass ratio W of the polyester resin to the vinyl resin in the white toner particles and the mass ratio C of the polyester resin to the vinyl resin in the color toner particles does not satisfy 0≦WC≦4. <7> According to the invention, there is provided a toner set for developing electrostatic images, which, when a cross section of a white toner particle is observed, has higher color development in an image having a colored image on a white image, and is less susceptible to peeling of the image when folded, compared to a case in which the ratio of white colorants having a particle size of 100 nm or less to all white colorants exceeds 30% by number. <8> According to the invention, there is provided a toner set for developing electrostatic images, which, when a cross section of a white toner particle is observed, has higher color development in an image having a colored image on a white image, and is less susceptible to peeling of the image when folded, as compared to a case in which the ratio of white colorants having a particle size of 100 nm or less to all white colorants exceeds 20% by number.

[0010] <9> , <10> , <11> , <12> or <13> According to the invention, there is provided an electrostatic image developer set, a toner cartridge set, a process cartridge, an image forming apparatus, or an image forming method, which comprises a white toner having white toner particles containing a polyester resin and a white colorant, and a non-white colored toner having colored toner particles containing a vinyl resin, a polyester resin, and a colored colorant, and which has a mass ratio C of the polyester resin to the vinyl resin in the colored toner particles that is less than 0.7 or more than 10, and when a cross section of the colored toner particles is observed, the area ratio of the white colorant is less than 10% or more than 50%, or the number average particle diameter of the white colorant is less than 0.23 μm or more than 0.45 μm, and which has high color development of an image having a colored image on a white image and suppresses peeling of the image when folded, compared to a case where a toner set for developing an electrostatic image is applied, in which the mass ratio C of the polyester resin to the vinyl resin in the colored toner particles is less than 0.7 or more than 10, and peeling of the image when folded is suppressed. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram illustrating an example of a process cartridge according to the present embodiment. [Diagram 3] FIG. 2 is a schematic diagram showing an example of a screw extruder used in the kneading and pulverizing method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the present invention will be described. These descriptions and examples are merely illustrative of the embodiments, and are not intended to limit the scope of the present invention.

[0013] In this embodiment, the numerical range indicated using "~" indicates a range that includes the numerical values ​​before and after "~" as the minimum and maximum values, respectively. In the numerical ranges described in the present embodiment, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in the present embodiment. In addition, in the numerical ranges described in the present embodiment, the upper or lower limit of the numerical range may be replaced with a value shown in the examples.

[0014] In this embodiment, the term "process" includes not only an independent process, but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved.

[0015] When the embodiment is described with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. Furthermore, the size of the members in each drawing is conceptual, and the relative relationship between the sizes of the members is not limited to this.

[0016] In this embodiment, each component may contain multiple types of corresponding substances. When referring to the amount of each component in the composition in this embodiment, if multiple types of substances corresponding to each component are present in the composition, the amount refers to the total amount of the multiple types of substances present in the composition, unless otherwise specified.

[0017] In the present embodiment, the term "(meth)acrylic" means either "acrylic" or "methacrylic".

[0018] In this embodiment, the "white toner for developing electrostatic images" is also referred to simply as "white toner", the "color toner for developing electrostatic images" is also referred to simply as "color toner", the "white developer for electrostatic images" is also referred to simply as "white developer", and the "color developer for electrostatic images" is also referred to simply as "color developer". In this embodiment, the "toner set for developing electrostatic images" is also simply referred to as a "toner set", and the "electrostatic image developer set" is also simply referred to as a "developer set".

[0019] <Toner set for developing electrostatic images> The toner set according to this embodiment includes a white toner having white toner particles containing a polyester resin and a white colorant, and a non-white color toner having color toner particles containing a vinyl resin, a polyester resin, and a color colorant. In the color toner particles, the mass ratio C of the polyester resin to the vinyl resin is 0.7 or more and 10 or less. In addition, when the cross section of the white toner particle is observed, the area ratio of the white colorant is 10% or more and 50% or less, and the number average particle diameter of the white colorant is 0.23 μm or more and 0.45 μm or less.

[0020] The toner set according to the present embodiment, due to the above-mentioned configuration, has high color development in an image having a color image on a white image, and peeling of the image when folded is suppressed. The reason for this is presumed to be as follows.

[0021] When forming images on recording media such as colored paper such as black paper, or film such as beverage labels, there is a use in which a white image is used as a base and a colored image is then formed on top of it in order to enhance the color development of the colored image. A combination is known in which the binder resin of the white toner particles contains a polyester resin, and the binder resin of the colored toner particles contains a vinyl resin (styrene acrylic resin, etc.) and a polyester resin. The reason for this is that the use of polyester resin in the white toner makes it easier to disperse the white colorant, and the use of vinyl resin, which does not easily lose charge under high temperature and high humidity conditions, in combination with polyester resin, which has excellent fixing properties, in the colored toner achieves a balance.

[0022] However, in a combination in which the binder resin of the white toner particles contains a polyester resin and the binder resin of the color toner particles contains a vinyl resin (such as a styrene acrylic resin) and a polyester resin, the components of the white toner particles and the color toner particles are difficult to dissolve in each other during fixing, and the adhesion of the color image to the white image is low. Therefore, when a recording medium that is expected to be folded, such as a film, is folded, peeling of the color image occurs. On the other hand, if the components of the white toner particles and the color toner particles are too compatible with each other during fixing, the components of the white toner particles and the color toner particles will be mixed excessively, causing color mixing and reducing the color development of the color image.

[0023] Therefore, in the toner set according to this embodiment, the mass ratio C of the polyester resin to the vinyl resin in the color toner particles is set to 0.7 or more and 10 or less. At the above mass ratio C, the color toner particles containing vinyl resin and polyester resin as binder resins contain a moderate amount of vinyl resin with low fixability and polyester resin that causes mixing with the white toner components. Therefore, during fixing, the affinity between the white toner particles and the color toner particles becomes appropriate, realizing sufficient fixing while suppressing excessive mixing of the components of the white toner particles and the color toner particles.

[0024] In addition, when the cross section of a white toner particle is observed, the area ratio of the white colorant is 10% or more and 50% or less, and the number average particle size of the white colorant is 0.23 μm or more and 0.45 μm or less. Polyester resin melts at a lower viscosity than vinyl resin, but by containing a white colorant in an appropriate amount and size within the above range together with the polyester resin in the white toner particles, the filler effect of the white colorant makes the white toner particles have a melt viscosity at the fixing temperature that makes them compatible with a small amount of polyester resin in the color toner particles. As a result, the white toner particles and the color toner particles are compatible with each other during fixing, but excessive compatibility is suppressed. Therefore, the resins of the white image and the color image are compatible with each other at the interface, resulting in high adhesion, while the components are not excessively mixed, making it difficult to crack when folded. As a result, the color development of the color image is maintained, and image peeling during folding is suppressed.

[0025] From the above, it is presumed that the toner set according to this embodiment has high color development for an image having a color image on a white image, and peeling of the image when folded is suppressed.

[0026] The toner set according to this embodiment will be described in detail below.

[0027] <Resin Amount of White Toner and Color Toner> (mass ratio C) In the color toner particles, the mass ratio C of the polyester resin to the vinyl resin is 0.7 or more and 10 or less. If the mass ratio C is less than 0.7, the vinyl resin ratio in the color toner particles becomes too high, making it difficult for the white toner particles and the color toner particles to become compatible with each other during fixing, and reducing the adhesion between the white image and the color image, which leads to increased image peeling when folded. If the mass ratio C exceeds 10, the polyester resin ratio in the color toner particles becomes too high, and the polyester resin in the white toner particles is mixed too much during fixing, resulting in mixing of the white colorant and the colored colorant, and the dispersibility of the white pigment is deteriorated, resulting in a decrease in the color development of the color image. From the viewpoints of suppressing peeling of an image and improving color development of an image, the mass ratio C is preferably 2 or more and 6 or less, and more preferably 3 or more and 5 or less.

[0028] (Relationship between mass ratio C and mass ratio W) When the white toner particles contain a vinyl resin, it is preferable that the relationship between the mass ratio W of the polyester resin to the vinyl resin in the white toner particles and the mass ratio C of the polyester resin to the vinyl resin in the color toner particles satisfies -0.6≦WC≦5.6. The relationship WC between the mass ratio W and the mass ratio C more preferably satisfies 0≦WC≦4, and further preferably satisfies 1≦WC≦3. When the relationship WC between the mass ratio W and the mass ratio C is within the above range, the relationship in the ratio of the vinyl resin and the polyester resin in the white toner particles and the colored toner particles becomes appropriate, and the polyester resin in the white toner particles and the colored toner particles are appropriately mixed during fixing, sufficiently improving the adhesion between the white image and the colored image, and suppressing a decrease in the color development of the colored image while easily suppressing image peeling when folded.

[0029] (Measurement of the content of each resin in toner particles) The content of each resin contained in the toner particles (white toner particles and color toner particles) is measured as follows.

[0030] First, each resin contained in the toner particles can be identified by known methods such as nuclear magnetic resonance measurement, infrared spectroscopy measurement, and pyrolysis gas chromatography mass spectrometry.

[0031] The content of each resin contained in the toner particles can be calculated by centrifugal separation and measurement of 1H-NMR spectrum by a nuclear magnetic resonance device.

[0032] The toner particles (or toner), the mass of which has been measured in advance, are dissolved in toluene, and then centrifuged to separate the resinous and non-resinous components. Next, the solution in which the resin is dissolved is collected, and the solvent is removed by drying to obtain the resin (i.e., solid) content. Then, the mass ratio of the resin content to the non-resin solid content is calculated from the mass of the resin content. Next, 10 mg of the resin was dissolved in 0.7 mL of deuterated chloroform solution, and tetramethylsilane (TMS) was added as a reference substance at a concentration of 0.05% by volume to prepare a measurement sample. Next, the measurement sample is subjected to 1H-NMR spectrum measurement using a nuclear magnetic resonance apparatus (JNM-AL400 (manufactured by JEOL Ltd.)). The measurement conditions are: standard substance: tetramethylsilane (TMS), temperature: 25°C, and number of accumulations: 128 times. Next, the obtained 1H-NMR spectrum is analyzed to determine the chemical shift and integral value ratio, and the molar ratio of each monomer constituting the resin is determined from the chemical shift and integral value ratio. Finally, the molar ratio is converted to a mass ratio by multiplying the molar ratio of each monomer by the molecular weight of the polymerized segment unit, thereby determining the content of each resin contained in the toner particles.

[0033] (Cross-sectional characteristics of white toner particles) When the cross section of a white toner particle is observed, the area ratio of the white colorant is 10% or more and 50% or less, and the number average particle diameter of the white colorant is 0.23 μm or more and 0.45 μm or less. If the area ratio of the white colorant exceeds 50% or the number average particle diameter exceeds 0.45 μm, the filler effect is difficult to exhibit, and the components of the white toner particles and the color toner particles are excessively compatible or mixed with each other during fixing, resulting in a decrease in the color development of the color image. If the area ratio of the white colorant is less than 10% or the number average particle size is less than 0.23 μm, the filler effect is exerted too much, making it difficult for the components of the white toner particles and the colored toner particles to be compatible with each other during fixing, and image peeling is likely to occur when the image is folded.

[0034] From the viewpoint of suppressing image peeling and improving the color development of a color image, the area ratio of the white colorant is preferably from 20% to 50%, and more preferably from 30% to 40%. From the same viewpoint, the number average particle size of the white colorant is preferably 0.23 μm or more and 0.30 μm or less, and more preferably 0.26 μm or more and 0.30 μm or less.

[0035] The area ratio and number-average particle diameter of the white colorant can be adjusted by, for example, using a colorant in which two or more white colorants having different particle diameters are mixed in advance in a kneading and grinding method described below, and adjusting the particle diameters and mixing ratio of the two or more white colorants having different particle diameters.

[0036] (Particle size distribution of white colorant) When the cross section of a white toner particle is observed, the ratio of white colorants having a particle size of 100 nm or less to all white colorants is preferably 30% by number or less, more preferably 20% by number, and even more preferably 18% by number. When the ratio of the white colorant having a particle size of 100 nm or less is within the above range, the filler effect of the white colorant makes the viscosity of the white toner compatible with the small amount of polyester resin in the color toner at the fixing temperature, which suppresses peeling of the image when folded and also facilitates improvement in the color development of the image.

[0037] The method for measuring the area ratio, number average particle diameter, and proportion of white colorant having a particle diameter of 100 nm or less is as follows. The white toner (or white toner) is mixed and embedded in an epoxy resin, and the epoxy resin is solidified. The solidified product is cut with an ultramicrotome (Ultracut UCT manufactured by Leica) to prepare a 250 nm thin section sample. Next, the cross section of the white toner particle of the thin sample is observed at 10,000 times magnification using a scanning transmission electron microscope (Hitachi High-Technologies Corporation: S-4800) to obtain a STEM image. Next, the STEM image is analyzed using an image processing analysis system (LUZEX AP manufactured by Nireco Corporation), and the white colorant in the white toner particles is binarized and identified. The conditions for binarization are to distinguish the white colorant and the binder resin based on color and shape, and the binarization process is performed using the midpoint between the brightness of the white colorant and the brightness of the binder resin as the threshold value.

[0038] Next, the areas of the white toner particle cross section and the white colorant on the image are obtained, and the area ratio of the white image to the white toner particle cross section is obtained. This operation is carried out for 10 white toner particles, and the arithmetic average value of the area ratio of the white colorant is calculated.

[0039] On the other hand, the circle-equivalent diameter of the white colorant on the image is obtained. Specifically, the area of ​​each particle is measured, and the circle-equivalent diameter is calculated from this area value. This operation is then carried out for 10 white toner particles, and the particle size distribution of the white colorant based on the number is obtained. In the obtained particle size distribution, the particle size at 50% of the cumulative number is defined as the number average particle size. In addition, in the obtained particle size distribution, the ratio (number %) of white colorants having a particle size of 100 nm or less to the total white colorant is determined.

[0040] <Composition of White Toner and Color Toner> Hereinafter, the components of the toners (white toner and color toners) included in the toner set according to this embodiment will be described. The toner in the present embodiment contains toner particles and may further contain an external additive.

[0041] Here, the term "color toner," "color toner particles," "color colorant," and "color image" refers to toner, toner particles, colorant, and image having a color other than white. For example, color toners include color toners such as yellow (Y), magenta (M), and cyan (C), and black (K) toner. For example, four toners, yellow, magenta, cyan, and black, may be used together to form a toner set with a white toner. In this case, it is preferable that at least one of the color toners satisfies the above conditions, and it is preferable that all the color toners used together satisfy the above conditions.

[0042] (Toner particles) The white toner particles contain a polyester resin as a binder resin and a white colorant. The white toner particles may contain a polyester resin and a vinyl resin as a binder resin. The color toner particles contain a vinyl resin and a polyester resin as a binder resin, and a color colorant. The toner particles (white toner particles and colored toner particles) may contain a release agent and other additives.

[0043] Each component will be described below.

[0044] -Binding resin- The polyester resin will now be described. The polyester resin may be, for example, a known amorphous polyester resin. The polyester resin may be used in combination with a crystalline polyester resin together with the amorphous polyester resin. However, the content of the crystalline polyester resin is preferably in the range of 2% by mass to 40% by mass (preferably 2% by mass to 20% by mass) based on the total binder resin.

[0045] The "crystalline" nature of a resin refers to the presence of a clear endothermic peak rather than a stepwise change in the amount of endothermic heat in differential scanning calorimetry (DSC); specifically, the half-width of the endothermic peak is within 10°C when measured at a heating rate of 10 (°C / min). On the other hand, the term "amorphous" for a resin refers to a half-width exceeding 10° C., a stepwise change in endothermic heat quantity, or no clear endothermic peak being observed.

[0046] Amorphous polyester resin The amorphous polyester resin may be, for example, a condensation polymer of a polyvalent carboxylic acid and a polyhydric alcohol. The amorphous polyester resin may be a commercially available product or a synthesized product.

[0047] Examples of polyvalent carboxylic acids include aliphatic dicarboxylic acids (e.g., oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenylsuccinic acid, adipic acid, sebacic acid, etc.), alicyclic dicarboxylic acids (e.g., cyclohexanedicarboxylic acid, etc.), aromatic dicarboxylic acids (e.g., terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, etc.), anhydrides thereof, and lower alkyl esters thereof (e.g., having 1 to 5 carbon atoms). Among these, aromatic dicarboxylic acids are preferable as polyvalent carboxylic acids. The polyvalent carboxylic acid may be a trivalent or higher carboxylic acid having a crosslinked or branched structure in combination with a dicarboxylic acid. Examples of the trivalent or higher carboxylic acid include trimellitic acid, pyromellitic acid, anhydrides thereof, and lower (e.g., carbon number 1 to 5) alkyl esters thereof. The polyvalent carboxylic acids may be used alone or in combination of two or more kinds.

[0048] Examples of polyhydric alcohols include aliphatic diols (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, etc.), alicyclic diols (e.g., cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, etc.), and aromatic diols (e.g., ethylene oxide adducts of bisphenol A, propylene oxide adducts of bisphenol A, etc.). Among these, examples of polyhydric alcohols include aromatic diols and alicyclic diols, and more preferably aromatic diols. As the polyhydric alcohol, a polyhydric alcohol having a crosslinked or branched structure of three or more may be used in combination with the diol. Examples of the polyhydric alcohol having a trihydric or higher valence include glycerin, trimethylolpropane, and pentaerythritol. The polyhydric alcohols may be used alone or in combination of two or more kinds.

[0049] The glass transition temperature (Tg) of the amorphous polyester resin is preferably 50°C or higher and 80°C or lower, and more preferably 50°C or higher and 65°C or lower. The glass transition temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC), more specifically, from the "extrapolated glass transition onset temperature" described in the method for determining glass transition temperature in JIS K 7121-1987 "Method for measuring transition temperature of plastics."

[0050] The weight average molecular weight (Mw) of the amorphous polyester resin is preferably 5,000 or more and 1,000,000 or less, and more preferably 7,000 or more and 500,000 or less. The number average molecular weight (Mn) of the amorphous polyester resin is preferably 2,000 or more and 100,000 or less. The molecular weight distribution Mw / Mn of the amorphous polyester resin is preferably 1.5 or more and 100 or less, and more preferably 2 or more and 60 or less. The weight average molecular weight and number average molecular weight are measured by gel permeation chromatography (GPC). The molecular weight measurement by GPC is performed using a Tosoh GPC HLC-8120GPC as the measuring device, a Tosoh TSKgel SuperHM-M (15 cm) column, and THF solvent. The weight average molecular weight and number average molecular weight are calculated from the measurement results using a molecular weight calibration curve created with a monodisperse polystyrene standard sample.

[0051] The amorphous polyester resin can be obtained by a known manufacturing method, for example, by carrying out the reaction while removing water and alcohol generated during condensation by setting the polymerization temperature to 180° C. or higher and 230° C. or lower, and reducing the pressure in the reaction system as necessary. If the raw material monomer is not soluble or compatible at the reaction temperature, a high boiling point solvent may be added as a solubilizing agent to dissolve it. In this case, the polycondensation reaction is carried out while distilling off the solubilizing agent. If a monomer with poor compatibility is present, it is recommended that the monomer with poor compatibility is condensed in advance with the acid or alcohol to be polycondensed, and then polycondensed with the main component.

[0052] Crystalline polyester resin The crystalline polyester resin may be, for example, a polycondensate of a polyvalent carboxylic acid and a polyhydric alcohol. The crystalline polyester resin may be a commercially available product or a synthesized product. Here, the crystalline polyester resin is preferably a polycondensate using a polymerizable monomer having a linear aliphatic group rather than a polymerizable monomer having an aromatic group, since the crystalline polyester resin can easily form a crystalline structure.

[0053] Examples of polyvalent carboxylic acids include aliphatic dicarboxylic acids (e.g., oxalic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, etc.), aromatic dicarboxylic acids (e.g., dibasic acids such as phthalic acid, isophthalic acid, terephthalic acid, naphthalene-2,6-dicarboxylic acid, etc.), anhydrides thereof, and lower alkyl esters thereof (e.g., having 1 to 5 carbon atoms). The polyvalent carboxylic acid may be a trivalent or higher carboxylic acid having a crosslinked or branched structure in combination with a dicarboxylic acid. Examples of the trivalent carboxylic acid include aromatic carboxylic acids (e.g., 1,2,3-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, etc.), their anhydrides, and their lower alkyl esters (e.g., carbon number 1 to 5). As the polyvalent carboxylic acid, a dicarboxylic acid having a sulfonic acid group and a dicarboxylic acid having an ethylenic double bond may be used in combination with these dicarboxylic acids. The polyvalent carboxylic acids may be used alone or in combination of two or more kinds.

[0054] Examples of polyhydric alcohols include aliphatic diols (for example, straight-chain aliphatic diols having 7 to 20 carbon atoms in the main chain). Examples of aliphatic diols include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, and 1,14-eicosanedecanediol. Among these, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol are preferred as aliphatic diols. The polyhydric alcohol may be a trihydric or higher alcohol having a crosslinked or branched structure in combination with the diol. Examples of the trihydric or higher alcohol include glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol. The polyhydric alcohols may be used alone or in combination of two or more kinds.

[0055] Here, the polyhydric alcohol has an aliphatic diol content of 80 mol % or more, preferably 90 mol % or more.

[0056] The melting temperature of the crystalline polyester resin is preferably 50°C or higher and 100°C or lower, more preferably 55°C or higher and 90°C or lower, and even more preferably 60°C or higher and 85°C or lower. The melting temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC) based on the "melting peak temperature" described in the method for determining melting temperature in JIS K7121-1987 "Method for measuring transition temperature of plastics."

[0057] The weight average molecular weight (Mw) of the crystalline polyester resin is preferably 6,000 or more and 35,000 or less.

[0058] The crystalline polyester resin can be obtained by a known manufacturing method, for example, in the same manner as the amorphous polyester.

[0059] The vinyl resin will now be described. Examples of vinyl resins include homopolymers of monomers such as styrenes (e.g., styrene, parachlorostyrene, α-methylstyrene, etc.), (meth)acrylic acid esters (e.g., methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, etc.), ethylenically unsaturated nitriles (e.g., acrylonitrile, methacrylonitrile, etc.), vinyl ethers (e.g., vinyl methyl ether, vinyl isobutyl ether, etc.), vinyl ketones (e.g., vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone, etc.), and olefins (e.g., ethylene, propylene, butadiene, etc.), or vinyl-based resins made of copolymers of two or more of these monomers in combination. These vinyl resins may be used alone or in combination of two or more.

[0060] As the vinyl resin, a styrene-acrylic resin is preferred from the viewpoints of charge controllability, color development of colored images, and suppression of image peeling. Styrene-acrylic resin is a copolymer obtained by copolymerizing at least a styrene-based monomer (a monomer having a styrene skeleton) and a (meth)acrylic monomer (a monomer having a (meth)acryloyl group, preferably a monomer having a (meth)acryloyloxy group). Styrene-acrylic resin includes, for example, a copolymer of a styrene monomer and the above-mentioned (meth)acrylic acid ester monomer. The acrylic resin portion in the styrene-acrylic resin is either an acrylic monomer or a methacrylic monomer, or a partial structure obtained by polymerizing them. In addition, "(meth)acrylic" is an expression that includes both "acrylic" and "methacrylic".

[0061] Specific examples of styrene-based monomers include styrene, alkyl-substituted styrenes (e.g., α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, etc.), halogen-substituted styrenes (e.g., 2-chlorostyrene, 3-chlorostyrene, 4-chlorostyrene, etc.), vinylnaphthalene, etc. The styrene-based monomers may be used alone or in combination of two or more. Of these, as the styrene-based monomer, styrene is preferred from the viewpoints of ease of reaction, ease of reaction control, and availability.

[0062] Specific examples of the (meth)acrylic monomer include (meth)acrylic acid and (meth)acrylic acid esters. Examples of the (meth)acrylic acid esters include (meth)acrylic acid alkyl esters (e.g., methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, n-lauryl (meth)acrylate, n-tetradecyl (meth)acrylate, n-hexadecyl (meth)acrylate, n-octadecyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, isopentyl (meth)acrylate, amyl (meth)acrylate, and (meth) Examples of the (meth)acrylic acid monomer include neopentyl acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, etc.), aryl (meth)acrylate esters (e.g., phenyl (meth)acrylate, biphenyl (meth)acrylate, diphenylethyl (meth)acrylate, t-butylphenyl (meth)acrylate, terphenyl (meth)acrylate, etc.), dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, methoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, β-carboxyethyl (meth)acrylate, and (meth)acrylamide. The (meth)acrylic acid monomer may be used alone or in combination of two or more. Among these (meth)acrylic esters among the (meth)acrylic monomers, from the viewpoint of enhancing the fixing property of the toner, (meth)acrylic esters having an alkyl group having 2 to 14 carbon atoms (preferably 2 to 10 carbon atoms, more preferably 3 to 8 carbon atoms) are preferred. Among these, n-butyl (meth)acrylate is preferred, and n-butyl acrylate is particularly preferred.

[0063] The copolymerization ratio of the styrene monomer to the (meth)acrylic monomer (mass basis, styrene monomer / (meth)acrylic monomer) is not particularly limited, but is preferably 98 / 2 to 60 / 40.

[0064] The styrene-acrylic resin may have a crosslinked structure. A preferred example of the styrene-acrylic resin having a crosslinked structure is a copolymer of at least a styrene-based monomer, a (meth)acrylic acid-based monomer, and a crosslinkable monomer.

[0065] The crosslinkable monomer may, for example, be a bifunctional or higher functional crosslinking agent. Examples of bifunctional crosslinking agents include divinylbenzene, divinylnaphthalene, di(meth)acrylate compounds (e.g., diethylene glycol di(meth)acrylate, methylene bis(meth)acrylamide, decanediol diacrylate, glycidyl (meth)acrylate, etc.), polyester type di(meth)acrylate, 2-([1'-methylpropylideneamino]carboxyamino)ethyl methacrylate, etc. Examples of trifunctional or higher crosslinking agents include tri(meth)acrylate compounds (e.g., pentaerythritol tri(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, etc.), tetra(meth)acrylate compounds (e.g., pentaerythritol tetra(meth)acrylate, oligoester (meth)acrylate, etc.), 2,2-bis(4-methacryloxy, polyethoxyphenyl)propane, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, triallyl trimellitate, diaryl chlorendate, etc. Among these, as the crosslinkable monomer, from the viewpoint of improving the fixing property of the toner, a bifunctional or higher (meth)acrylate compound is preferable, a bifunctional (meth)acrylate compound is more preferable, a bifunctional (meth)acrylate compound having an alkylene group having 6 to 20 carbon atoms is further preferable, and a bifunctional (meth)acrylate compound having a linear alkylene group having 6 to 20 carbon atoms is particularly preferable.

[0066] The copolymerization ratio of the crosslinkable monomer to the total monomers (mass basis, crosslinkable monomer / total monomers) is not particularly limited, but is preferably 2 / 1,000 to 20 / 1,000.

[0067] The glass transition temperature (Tg) of the styrene-acrylic resin is preferably from 40° C. to 75° C., more preferably from 50° C. to 65° C., from the viewpoint of improving the fixing property of the toner.

[0068] Here, the glass transition temperature of the resin is determined from a DSC curve obtained by differential scanning calorimetry (DSC). More specifically, the glass transition temperature of the resin is determined from the "extrapolated glass transition onset temperature" described in the method for determining glass transition temperature in JIS K 7121:1987 "Method for measuring transition temperature of plastics."

[0069] From the viewpoint of storage stability of the toner, the weight average molecular weight of the styrene-acrylic resin is preferably from 5,000 to 200,000, more preferably from 10,000 to 100,000, and particularly preferably from 20,000 to 80,000.

[0070] Here, the weight average molecular weight and number average molecular weight of the resin are measured by gel permeation chromatography (GPC). The molecular weight measurement by GPC is performed using a Tosoh GPC HLC-8120GPC as the measuring device, a Tosoh TSKgel SuperHM-M (15 cm) column, and THF solvent. The weight average molecular weight and number average molecular weight are calculated from the measurement results using a molecular weight calibration curve created with a monodisperse polystyrene standard sample.

[0071] The method for producing the styrene-acrylic resin is not particularly limited, and various polymerization methods (e.g., solution polymerization, precipitation polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc.) are applied. In addition, the polymerization reaction is carried out by a known operation (e.g., batchwise, semi-continuous, continuous, etc.).

[0072] Here, the coexistence of styrene-acrylic resin and polyester resin can be achieved not only by mixing the respective resins, but also as a chemically bonded hybrid resin having a styrene-acrylic resin segment and a polyester resin segment (so-called styrene-acrylic modified polyester resin). Specifically, a hybrid resin can be obtained by polymerizing a polyester monomer having an unsaturated structure such as fumaric acid or succinic acid or a resin containing the monomer structure as a prepolymer and polymerizing it with a vinyl monomer such as styrene or acrylic. When a hybrid resin (a so-called styrene-acrylic modified polyester resin) is used, the mass ratios C and W of the polyester resin to the vinyl resin are measured and calculated as the mass ratio of the polyester segment to the vinyl resin segment (e.g., styrene-acrylic resin segment) of the hybrid resin. When a hybrid resin, a vinyl resin (e.g., styrene-acrylic resin) and a polyester resin are used in combination, the mass ratios C and W are measured and calculated as the mass ratio of the sum of the polyester resin segment and the polyester resin of the hybrid resin to the sum of the vinyl resin segment and the vinyl resin of the hybrid resin.

[0073] -Coloring agent- In the case of white toner particles, a white colorant is applied, and in the case of colored toner particles, a colored colorant other than the white colorant is applied. However, in the case of white toner particles, if the toner particles contain 15% by mass or more of a white colorant, the toner particles are considered to be white toner even if they contain a colored colorant.

[0074] --White colorant-- The white colorant may be an inorganic pigment or an organic pigment. Specific examples of the white colorant include inorganic pigments such as heavy calcium carbonate, light calcium carbonate, titanium dioxide, aluminum hydroxide, satin 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, and smexite, and organic pigments such as polystyrene resin particles and urea formalin resin particles. In particular, from the viewpoint of forming a white image having higher hiding power and superior color to a colored image, the white colorant is preferably at least one selected from the group consisting of titanium oxide, silicon dioxide, aluminum oxide, zinc oxide, and zirconium oxide.

[0075] In particular, titanium oxide is preferred as the white colorant from the viewpoint of excellent hiding power. The crystal structure of titanium oxide may be any of anatase type, rutile type, and brookite type.

[0076] The white colorant may be surface-treated as necessary, and may be used in combination with a dispersant.

[0077] The number average particle diameter of the white colorant measured by itself (hereinafter also referred to as "number average particle diameter Dcc of the white colorant alone") is preferably 150 nm or more and 900 nm or less from the viewpoint of excellent hiding power. The number-average particle diameter Dcc of the white colorant alone is calculated by adding 100 mg of the white colorant to 10 ml of a 1:1 mixture of water and ethanol, dispersing the mixture in an ultrasonic cleaner, dropping one drop of the dispersion onto a mesh for STEM observation and immediately blowing it off with a blower to dry it, observing the result with a scanning electron microscope SEM (Hitachi High-Tech Corp.: S-4800) and taking an image, and importing this image into an image analyzer (Nireco Corp.: LUZEX AP) and performing image analysis. Specifically, the area of ​​each particle is measured, and the equivalent circle diameter is calculated from this area value. Specifically, an electron microscope is adjusted so that 10 to 50 particles of the white colorant are captured in one field of view, and images are taken, the area of ​​each particle is determined by image analysis, and the equivalent circle diameter is calculated from this area value. The average of the equivalent circle diameters of 100 particles in multiple fields of view is taken as the number-average particle diameter Dcc of the white colorant alone.

[0078] The white colorant may be used alone or in combination of two or more kinds.

[0079] The content of the white colorant is preferably from 15% by mass to 65% by mass, more preferably from 20% by mass to 60% by mass, and even more preferably from 30% by mass to 50% by mass, based on the total amount of the white toner particles. When the content of the white colorant is within the above range, the reflectance of the white image is increased while image peeling is suppressed, and the color development of the color image is easily improved.

[0080] --Colored dyes-- Examples of colored colorants include carbon black, chrome yellow, Hansa Yellow, benzidine yellow, threne yellow, quinoline yellow, pigment yellow, permanent orange GTR, pyrazolone orange, Balkan orange, watch young red, permanent red, brilliant carmine 3B, brilliant carmine 6B, DuPont oil red, pyrazolone red, lithol red, rhodamine B lake, lake red C, pigment red, rose bengal, aniline blue, ultra Examples of the pigments include marine blue, chalcoil blue, methylene blue chloride, phthalocyanine blue, pigment blue, phthalocyanine green, and malachite green oxalate, as well as various dyes such as acridine-based, xanthene-based, azo-based, benzoquinone-based, azine-based, anthraquinone-based, thioindigo-based, dioxazine-based, thiazine-based, azomethine-based, indigo-based, phthalocyanine-based, aniline black-based, polymethine-based, triphenylmethane-based, diphenylmethane-based, and thiazole-based dyes. The coloring agent may be used alone or in combination of two or more kinds.

[0081] The content of the color colorant is, for example, preferably from 1% by mass to 30% by mass, and more preferably from 3% by mass to 15% by mass, based on the total amount of the color toner particles.

[0082] -Release agent- Examples of the release agent include hydrocarbon waxes; natural waxes such as carnauba wax, rice wax, and candelilla wax; synthetic or mineral / petroleum waxes such as montan wax; and ester waxes such as fatty acid esters and montan acid esters. The release agent is not limited to these. The release agent for the colored toner particles is preferably an ester wax.

[0083] -Other additives- Examples of other additives include known additives such as magnetic materials, charge control agents, inorganic powders, etc. These additives are contained in the toner particles as internal additives. -Characteristics of toner particles, etc.- The toner particles may be toner particles having a single layer structure, or may be toner particles having a so-called core-shell structure composed of a core portion (core particle) and a coating layer (shell layer) that coats the core portion. Here, the toner particles having a core-shell structure may be composed of, for example, a core containing a binder resin and, if necessary, other additives such as a colorant and a release agent, and a coating layer containing the binder resin.

[0084] The volume average particle size of the toner particles has a suitable range for each of the white toner particles and the color toner particles. Volume average particle size of white toner particles D W is preferably 5.0 μm or more and 10.0 μm or less, and more preferably 6.0 μm or more and 9.0 μm or less. Volume average particle size of color toner particles D W is preferably 3.0 μm or more and 8.0 μm or less, and more preferably 4.0 μm or more and 7.0 μm or less.

[0085] The volume average particle size of the toner particles is measured using a Coulter Multisizer II (manufactured by Beckman Coulter, Inc.), and the electrolyte is measured using an ISOTON-II (manufactured by Beckman Coulter, Inc.). For the measurement, 0.5 mg to 50 mg of the measurement sample is added to 2 ml of a 5% aqueous solution of a surfactant (preferably sodium alkylbenzene sulfonate) as a dispersant, and this is then added to 100 ml to 150 ml of the electrolyte. The electrolyte with the sample suspended in it is dispersed for 1 minute using an ultrasonic disperser, and the particle size distribution of particles with diameters in the range of 2 μm to 60 μm is measured using a Coulter Multisizer II with an aperture diameter of 100 μm. The number of particles sampled is 50,000. Based on the measured particle size distribution, cumulative distributions of volume and number are drawn for each divided particle size range (channel) from the smallest diameter side, and the particle size at 16% of the cumulative total is defined as the volume particle size D16v, the number particle size D16p, and the particle size at 50% of the cumulative total as the volume average particle size D50v.

[0086] The average circularity of the toner particles is preferably 0.90 or more and 1.00 or less, and more preferably 0.92 or more and 0.98 or less.

[0087] The average circularity of toner particles is calculated by (circular equivalent perimeter) / (perimeter) [(perimeter of a circle having the same projected area as the particle image) / (perimeter of the particle projected image)]. Specifically, it is a value measured by the following method. First, the toner particles to be measured are sucked and collected, flattened, and a still image of the particles is captured by instantaneous strobe light emission, and the particle image is analyzed by a flow-type particle image analyzer (FPIA-3000 manufactured by Sysmex Corporation). The number of samples to be taken in order to calculate the average circularity is 3,500. When the toner contains an external additive, the toner (developer) to be measured is dispersed in water containing a surfactant, and then ultrasonic treatment is performed to obtain toner particles from which the external additive has been removed.

[0088] (External additives) Examples of the external additive include inorganic particles. Examples of the inorganic particles include SiO2, TiO2, SrTiO3, Al2O3, CuO, ZnO, SnO2, CeO2, Fe2O3, MgO, BaO, CaO, K2O, Na2O, ZrO2, CaO·SiO2, K2O·(TiO2)n, Al2O3·2SiO2, CaCO3, MgCO3, BaSO4, MgSO4, etc. SiO2 is preferred from the viewpoint of suppressing peeling of colored images, increasing the light scattering property of white images, and facilitating improvement in color development of colored images.

[0089] The surface of the inorganic particles as an external additive may be subjected to a hydrophobic treatment. The hydrophobic treatment may be performed, for example, by immersing the inorganic particles in a hydrophobic treatment agent. The hydrophobic treatment agent is not particularly limited, and examples thereof include silane coupling agents, silicone oils, titanate coupling agents, and aluminum coupling agents. These may be used alone or in combination of two or more. The amount of the hydrophobizing agent is usually, for example, 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the inorganic particles.

[0090] Examples of external additives include resin particles (resin particles such as polystyrene, polymethyl methacrylate (PMMA), and melamine resin), cleaning agents (for example, metal salts of higher fatty acids such as zinc stearate, and fluorine-based polymer particles).

[0091] The amount of the external additive added is, for example, preferably from 0.01% by mass to 10% by mass, and more preferably from 0.01% by mass to 6.0% by mass, based on the toner particles.

[0092] (Toner manufacturing method) Next, a method for producing the toner (white toner and color toner) according to this embodiment will be described. The toner according to the exemplary embodiment is obtained by producing toner particles and then externally adding an external additive to the toner particles.

[0093] The toner particles may be produced by any of a dry production method (e.g., a kneading and pulverizing method, etc.) and a wet production method (e.g., an aggregation-coalescence method, a suspension polymerization method, a dissolution suspension method, etc.). The method for producing the toner particles is not particularly limited, and a well-known production method is adopted.

[0094] Among these, white toner particles are preferably produced by the kneading and pulverizing method, while colored toner particles are preferably produced by the aggregation and coalescence method.

[0095] Hereinafter, examples of the kneading and pulverizing method and the aggregation and coalescence method will be described. However, in the description of each method, no distinction is made between colors.

[0096] (Kneading and grinding method) The kneading and pulverizing method is a method for obtaining toner particles through a kneading step in which toner particle forming materials (i.e., binder resin, colorant, etc.) are melted and kneaded to obtain a kneaded mixture, and a pulverizing step in which the obtained kneaded mixture is pulverized.

[0097] -Kneading process- In the kneading step, toner particle forming materials including a binder resin, a white colorant, etc. may be kneaded. The toner particle forming materials may contain other additives such as a release agent, if necessary. In the kneading step, it is preferable to add 0.5 parts by mass to 5 parts by mass of an aqueous medium (for example, water such as distilled water or ion-exchanged water, alcohols, etc.) to 100 parts by mass of the toner particle forming material.

[0098] Examples of the kneader used in the kneading step include a single screw extruder, a twin screw extruder, etc. Below, as an example of the kneader, a kneader having a feed screw section and two kneading sections will be described with reference to the drawings, but the kneader is not limited thereto.

[0099] As shown in FIG. 3, the screw extruder 11 includes a barrel 12 equipped with a screw (not shown), an inlet 14 for injecting a toner particle forming material, which is the raw material of the toner, into the barrel 12, a liquid addition inlet 16 for adding an aqueous medium to the toner particle forming material in the barrel 12, and a discharge outlet 18 for discharging a kneaded product formed by kneading the toner particle forming material in the barrel 12.

[0100] Barrel 12 is divided into, from the side closest to injection port 14, a feed screw section SA that transports the toner particle forming material injected from injection port 14 to kneading section NA, kneading section NA for melting and kneading the toner particle forming material in a first kneading process, a feed screw section SB that transports the toner particle forming material melted and kneaded in kneading section NA to kneading section NB, kneading section NB that melts and kneads the toner particle forming material in a second kneading process to form a kneaded material, and a feed screw section SC that transports the formed kneaded material to discharge port 18.

[0101] A different temperature control device (not shown) is provided for each block inside the barrel 12. That is, the blocks 12A to 12J may be configured to be controlled at different temperatures. 3 shows a state in which the temperatures of blocks 12A and 12B are controlled to t0° C., the temperatures of blocks 12C to 12E are controlled to t1° C., and the temperatures of blocks 12F to 12J are controlled to t2° C. Therefore, the toner particle forming material in the kneading unit NA is heated to t1° C., and the toner particle forming material in the kneading unit NB is heated to t2° C.

[0102] When the toner particle forming material is supplied to the barrel 12 from the inlet 14, the toner particle forming material is sent to the kneading section NA by the feed screw section SA. At this time, since the temperature of the block 12C is set to t1°C, the toner particle forming material is heated and changed to a molten state and sent to the kneading section NA in that state. Since the temperatures of the blocks 12D and 12E are also set to t1°C, the toner particle forming material is melted and kneaded at a temperature of t1°C in the kneading section NA. The binder resin and the release agent are in a molten state in the kneading section NA and are sheared by the screw.

[0103] Next, the toner particle forming material kneaded in the kneading section NA is sent to the kneading section NB by the feed screw section SB. Next, in the feed screw section SB, the aqueous medium is added to the toner particle forming material by injecting the aqueous medium into the barrel 12 through the liquid addition port 16. Although the embodiment shows the aqueous medium being injected in the feed screw section SB, the present invention is not limited thereto, and the aqueous medium may be injected in the kneading section NB, or may be injected in both the feed screw section SB and the kneading section NB. In other words, the position and the injection location for injecting the aqueous medium are selected as necessary.

[0104] When the aqueous medium is injected into the barrel 12 through the liquid addition port 16, the toner particle forming material in the barrel 12 is mixed with the aqueous medium, and the toner particle forming material is cooled by the latent heat of evaporation of the aqueous medium, thereby maintaining the temperature of the toner particle forming material. Finally, the kneaded material formed by melt-kneading in the kneading section NB is transported to the discharge port 18 by the feed screw section SC, and is discharged from the discharge port 18. In the manner described above, the kneading step using the screw extruder 11 shown in FIG. 1 is carried out.

[0105] -Cooling process- The cooling step is a step of cooling the molten kneaded product formed in the melt-kneading step. In the cooling step, it is preferable to cool the kneaded product at a temperature at the end of the kneading step to 40°C or less at an average temperature drop rate of 4°C / sec or more. If the cooling rate of the kneaded product is slow, the mixture (a mixture of the binder resin, the colorant, etc.) finely dispersed in the binder resin in the kneading step may recrystallize and the dispersion diameter may become large. On the other hand, if the kneaded product is rapidly cooled at the average temperature drop rate, the dispersion state immediately after the end of the kneading step is maintained as it is, which is preferable. The average temperature drop rate refers to the average value of the rate at which the temperature of the kneaded product at the end of the kneading step (for example, t2°C when the screw extruder 11 in FIG. 3 is used) is lowered to 40°C. Specific examples of the cooling method in the cooling step include a method using a rolling roll in which cold water or brine is circulated and a pinching cooling belt. When cooling is performed by the above method, the cooling rate is determined by the speed of the rolling roll, the flow rate of the brine, the supply amount of the kneaded material, the slab thickness when the kneaded material is rolled, etc. The slab thickness is preferably 1 mm or more and 3 mm or less.

[0106] -Crushing process- The kneaded material cooled in the cooling step is pulverized in the pulverization step to form particles. In the pulverization step, for example, a mechanical pulverizer, a jet pulverizer, etc. are used. If necessary, the particles may be heat-treated with hot air or the like to be spheroidized.

[0107] -Classification process- The particles obtained in the pulverization step may be classified in a classification step, if necessary, to obtain toner particles having a volume average particle diameter in a desired range. In the classification step, a conventional centrifugal classifier, an inertial classifier, or the like is used to remove fine powder (particles smaller than the desired particle diameter range) and coarse powder (particles larger than the desired particle diameter range).

[0108] Through the above steps, toner particles are obtained.

[0109] (agglomeration coalescence method) The aggregation and coalescence method can be, for example, A step of preparing each dispersion (a dispersion preparation step); a step of mixing a first resin particle dispersion liquid in which first resin particles serving as a binder resin are dispersed, a colorant dispersion liquid in which a colorant is dispersed, and a release agent particle dispersion liquid in which release agent particles (hereinafter also referred to as "release agent particles") are dispersed, and aggregating the particles and the colorant in the obtained dispersion liquid to form first aggregated particles (first aggregated particle forming step); a step of adding second resin particles serving as a binder resin to the first aggregated particle dispersion liquid after obtaining the first aggregated particle dispersion liquid in which the first aggregated particles are dispersed, and aggregating the second resin particles onto the surfaces of the first aggregated particles to form second aggregated particles (second aggregated particle forming step); a step of heating the second aggregate particle dispersion liquid in which the second aggregate particles are dispersed to fuse and coalesce the second aggregate particles to form toner particles (fusion and coalescence step); This is a method for producing toner particles through the steps of: The present aggregation-coalescence method will be described as a method for producing toner particles containing a binder resin, a colorant, and a release agent, and the release agent is a component that is included in the toner particles as necessary.

[0110] -Each dispersion preparation process- First, the various dispersions to be used in the aggregation-coalescence method are prepared. Specifically, a first resin particle dispersion in which the first resin particles to be the binder resin are dispersed, a colorant dispersion in which the colorant is dispersed, a second resin particle dispersion in which the second resin particles to be the binder resin are dispersed, and a release agent particle dispersion in which the release agent particles are dispersed are prepared. In each dispersion preparation step, the first resin particles and the second resin particles will be referred to as "resin particles" in the following description.

[0111] Here, the resin particle dispersion liquid is prepared, for example, by dispersing resin particles in a dispersion medium with the aid of a surfactant.

[0112] The dispersion medium used in the resin particle dispersion liquid is, for example, an aqueous medium. Examples of the aqueous medium include water such as distilled water and ion-exchanged water, alcohols, etc. These may be used alone or in combination of two or more.

[0113] Examples of the surfactant include anionic surfactants such as sulfate salts, sulfonates, phosphates, and soaps; cationic surfactants such as amine salts and quaternary ammonium salts; and nonionic surfactants such as polyethylene glycols, alkylphenol ethylene oxide adducts, and polyhydric alcohols. Among these, anionic surfactants and cationic surfactants are particularly preferred. The nonionic surfactants may be used in combination with anionic surfactants or cationic surfactants. The surfactant may be used alone or in combination of two or more kinds.

[0114] In the resin particle dispersion, examples of the method for dispersing the resin particles in the dispersion medium include general dispersion methods using, for example, a rotary shear type homogenizer, a ball mill having a media, a sand mill, a dyno mill, etc. Depending on the type of resin particles, the resin particles may be dispersed in the resin particle dispersion using, for example, a phase inversion emulsification method. The phase inversion emulsification method is a method in which the resin to be dispersed is dissolved in a hydrophobic organic solvent in which the resin is soluble, a base is added to the organic continuous phase (O phase) to neutralize it, and then an aqueous medium (W phase) is added to effect conversion of the resin from W / O to O / W (so-called phase inversion), resulting in a discontinuous phase, and the resin is dispersed in particulate form in the aqueous medium.

[0115] The volume average particle size of the resin particles dispersed in the resin particle dispersion is, for example, preferably from 0.01 μm to 1 μm, more preferably from 0.08 μm to 0.8 μm, and even more preferably from 0.1 μm to 0.6 μm. The volume average particle size of the resin particles is measured by using a particle size distribution obtained by measurement using a laser diffraction particle size distribution measuring device (e.g., LA-700 manufactured by Horiba, Ltd.), subtracting the cumulative distribution from the small particle size side for the volume of the divided particle size range (channel), and measuring the particle size at which the cumulative distribution is 50% of all particles as the volume average particle size D50v. The volume average particle sizes of particles in other dispersions are also measured in the same manner.

[0116] The content of the resin particles in the resin particle dispersion is, for example, preferably from 5% by mass to 50% by mass, and more preferably from 10% by mass to 40% by mass.

[0117] In addition, for example, a colorant dispersion and a release agent particle dispersion are also prepared in the same manner as the resin particle dispersion. That is, the volume average particle size, dispersion medium, dispersion method, and content of particles in the resin particle dispersion are the same for the colorant dispersed in the colorant dispersion and the release agent particles dispersed in the release agent particle dispersion.

[0118] -First agglomerated particle formation process- Next, the first resin particle dispersion liquid, the colorant dispersion liquid, and the release agent particle dispersion liquid are mixed together. Then, in this mixed dispersion, the first resin particles, the colorant, and the release agent particles are hetero-aggregated to form first aggregated particles containing the first resin particles, the colorant, and the release agent particles.

[0119] Specifically, for example, a coagulant is added to a dispersion liquid obtained by mixing a first resin particle dispersion liquid, a colorant dispersion liquid, and a release agent particle dispersion liquid, and the pH of the mixed dispersion liquid is adjusted to be acidic (for example, a pH of 2 or more and 5 or less), a dispersion stabilizer is added as necessary, and then the temperature is set to a range of 20°C or more and 50°C or less, and the particles dispersed in the mixed dispersion liquid are coagulated to form first coagulated particles. In the first aggregate particle formation step, for example, the above-mentioned aggregating agent may be added to the mixed dispersion at room temperature (e.g., 25°C) while stirring the mixed dispersion with a rotary shear homogenizer, the pH of the mixed dispersion may be adjusted to an acidic state (e.g., a pH of 2 or more and 5 or less), and a dispersion stabilizer may be added as necessary, followed by the above-mentioned heating.

[0120] Examples of the flocculant include a surfactant having a polarity opposite to that of the surfactant used as the dispersant added to the mixed dispersion, an inorganic metal salt, and a divalent or higher metal complex. In particular, when a metal complex is used as the flocculant, the amount of surfactant used is reduced and the charging characteristics are improved. If necessary, an additive that forms a complex or a similar bond with the metal ions of the flocculant may be used, and a chelating agent is preferably used as this additive.

[0121] Examples of inorganic metal salts include metal salts such as calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride, and aluminum sulfate, as well as inorganic metal salt polymers such as polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide. The chelating agent may be a water-soluble chelating agent, such as oxycarboxylic acid (e.g., tartaric acid, citric acid, gluconic acid, etc.), iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA), etc. The amount of the chelating agent added is, for example, preferably 0.01 parts by mass or more and 5.0 parts by mass or less, and more preferably 0.1 parts by mass or more and less than 3.0 parts by mass, relative to 100 parts by mass of the first resin particles.

[0122] -Second agglomerated particle formation process- Next, after obtaining the first aggregated particle dispersion liquid in which the first aggregated particles are dispersed, the second resin particle dispersion liquid in which the second resin particles are dispersed is added to the first aggregated particle dispersion liquid. The second resin particles may be of the same type as the first resin particles, or may be of a different type.

[0123] Then, in a dispersion liquid containing the first aggregated particles and the second resin particles, the second resin particles are aggregated on the surfaces of the first aggregated particles. At this time, a release agent particle dispersion liquid may also be added to aggregate the second resin particles and the release agent particles on the surfaces of the first aggregated particles. Specifically, for example, in the first aggregated particle forming step, when the first aggregated particles reach a target particle size, the second resin particle dispersion liquid is added to the first aggregated particle dispersion liquid, and heating is performed at a temperature equal to or lower than the glass transition temperature of the second resin particles. Then, the pH of the dispersion is adjusted to, for example, a range of about 6.5 to 8.5, thereby stopping the progress of aggregation. In this manner, the second aggregated particles are obtained, which are aggregated such that the second resin particles adhere to the surfaces of the first aggregated particles.

[0124] -Fusion / unification process- Next, the second aggregate particle dispersion liquid in which the second aggregate particles are dispersed is heated, for example, to a temperature equal to or higher than the glass transition temperature of the first and second resin particles (for example, a temperature 10 to 30° C. higher than the glass transition temperatures of the first and second resin particles) to fuse and coalesce the second aggregate particles, thereby forming toner particles.

[0125] Through the above steps, toner particles are obtained. In the above-described aggregation-coalescence method, the first aggregated particles may be fused and coalesced to form toner particles without carrying out the second aggregated particle forming step. Also, the second aggregated particle forming step may be repeated multiple times.

[0126] After the fusion and coalescence process, the toner particles formed in the solution are subjected to a known washing process, solid-liquid separation process, and drying process to obtain toner particles in a dried state. In the washing step, it is preferable to carry out sufficient replacement washing with ion-exchanged water from the viewpoint of electrostatic charge. In addition, the solid-liquid separation step is not particularly limited, but it is preferable to carry out suction filtration, pressure filtration, etc. from the viewpoint of productivity. In addition, there is no particular limit to the method for the drying step, but freeze drying, air flow drying, etc. are preferable from the viewpoint of productivity. It is advisable to carry out drying by a method such as drying with a rotary chuck, fluidized bed drying, or vibration-type fluidized bed drying.

[0127] In the toner production method according to the present embodiment, for example, an external additive may be added and mixed to the toner particles obtained by the above-described method for producing toner particles. The mixing may be carried out, for example, by using a V blender, a Henschel mixer, a Loedige mixer, etc. Furthermore, if necessary, coarse particles of the toner may be removed using a vibration sifter, a wind sifter, etc.

[0128] <Electrostatic image developer set> The electrostatic image developer set according to this embodiment includes a white electrostatic image developer containing a white toner contained in the toner set according to this embodiment, and a color electrostatic image developer containing a color toner contained in the toner set for developing electrostatic images according to this embodiment. In the electrostatic image developer set according to this embodiment, each developer may be a one-component developer containing only the toner in the toner set according to this embodiment, or may be a two-component developer in which the toner is mixed with a carrier.

[0129] The carrier is not particularly limited, and may be any known carrier, such as a coated carrier in which the surface of a core material made of magnetic powder is coated with a coating resin, a magnetic powder dispersion type carrier in which magnetic powder is dispersed and mixed in a matrix resin, or a resin impregnated type carrier in which porous magnetic powder is impregnated with a resin. The magnetic powder dispersion type carrier and the resin impregnated type carrier may be a carrier in which the constituent particles of the carrier are used as a core material and are coated with a coating resin.

[0130] Examples of the magnetic powder include magnetic metals such as iron, nickel, and cobalt, and magnetic oxides such as ferrite and magnetite.

[0131] Examples of the coating resin and matrix resin include styrene-acrylic resin; polyolefin resins such as polyethylene and polypropylene; polyvinyl or polyvinylidene resins such as polystyrene, (meth)acrylic resin, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, and polyvinyl ketone; vinyl chloride-vinyl acetate copolymer; straight silicone resin or modified product thereof consisting of organosiloxane bonds; fluororesins such as polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, and polychlorotrifluoroethylene; polyester; polyurethane; polycarbonate; amino resins such as urea-formaldehyde resin; and epoxy resins. The coating resin and the matrix resin preferably contain a (meth)acrylic resin, more preferably contain an alicyclic (meth)acrylic resin in an amount of 50 mass% or more relative to the total mass of the resin, and particularly preferably contain a (meth)acrylic resin in an amount of 80 mass% or more relative to the total mass of the resin. The coating resin and the matrix resin may contain other additives such as conductive particles. Examples of the conductive particles include particles of metals such as gold, silver, and copper, carbon black, titanium oxide, zinc oxide, tin oxide, barium sulfate, aluminum borate, and potassium titanate.

[0132] Here, in order to coat the surface of the core material with a coating resin, a method of coating with a coating layer forming solution in which the coating resin and, if necessary, various additives are dissolved in an appropriate solvent can be mentioned. The solvent is not particularly limited and may be selected taking into consideration the coating resin to be used, the suitability for application, etc. Specific resin coating methods include an immersion method in which the core material is immersed in a solution for forming a coating layer, a spray method in which the solution for forming a coating layer is sprayed onto the surface of the core material, a fluidized bed method in which the solution for forming a coating layer is sprayed onto the core material while it is suspended in flowing air, and a kneader coater method in which the core material of a carrier and the solution for forming a coating layer are mixed in a kneader coater and the solvent is removed.

[0133] In the two-component developer, the mixture ratio (mass ratio) of the toner and the carrier is preferably toner:carrier=1:100 to 30:100, and more preferably 3:100 to 20:100.

[0134] <Image forming device, image forming method> An image forming apparatus and an image forming method according to the present embodiment will be described. The image forming apparatus according to this embodiment includes a first developing means containing a white electrostatic image developer included in the developer set according to this embodiment, and a first image forming means for forming a white image, a second developing means containing a colored electrostatic image developer included in the developer set according to this embodiment, and a second image forming means for forming a colored image using colored toners, a transfer means for transferring the white image and the colored image onto the surface of a recording medium, and a fixing means for fixing the white image and the colored image transferred onto the surface of the recording medium. The image forming apparatus according to the present embodiment may be in a form including, as a first or second image forming means, image forming means each having an image holder, a charging means for charging the surface of the image holder, an electrostatic image forming means for forming an electrostatic image on the charged surface of the image holder, and a developing means for developing the electrostatic image formed on the surface of the image holder by an electrostatic image developer into a toner image. In addition, the image forming apparatus according to the present embodiment may have a configuration including an image carrier, a charging means for charging the surface of the image carrier, an electrostatic image forming means for forming an electrostatic image on the charged surface of the image carrier, and first and second developing means as first and second image forming means for developing the electrostatic image formed on the surface of the image carrier by an electrostatic image developer into a toner image.

[0135] In the image forming apparatus according to this embodiment, an image forming method (image forming method according to this embodiment) is carried out, which includes a first image forming process of forming a white image using a white toner of the toner set for developing electrostatic images according to this embodiment, a second image forming process of forming a colored image using a colored toner of the toner set for developing electrostatic images according to this embodiment, a transfer process of transferring the white image and the colored image onto a recording medium, and a fixing process of fixing the white image and the colored image onto the recording medium.

[0136] The image forming apparatus according to the present embodiment may be any of known image forming apparatuses, such as a direct transfer type apparatus that transfers a toner image (in the present embodiment, a white image or a colored image) formed on the surface of an image holder directly to a recording medium; an intermediate transfer type apparatus that performs primary transfer of a toner image formed on the surface of an image holder to the surface of an intermediate transfer body, and then performs secondary transfer of the toner image transferred to the surface of the intermediate transfer body to the surface of a recording medium; an apparatus equipped with a cleaning means that cleans the surface of the image holder before charging after the transfer of the toner image; and an apparatus equipped with a discharging means that irradiates the surface of the image holder with discharging light to discharge it before charging after the transfer of the toner image. In the case of an intermediate transfer type device, the transfer means has, for example, an intermediate transfer body onto whose surface a toner image is transferred, a primary transfer means which primarily transfers the toner image formed on the surface of the image carrier onto the surface of the intermediate transfer body, and a secondary transfer means which secondarily transfers the toner image transferred onto the surface of the intermediate transfer body onto the surface of a recording medium.

[0137] In the image forming apparatus according to the present embodiment, for example, a portion including the developing means may have a cartridge structure (process cartridge) that is detachably attached to the image forming apparatus. As the process cartridge, for example, a process cartridge equipped with a developing means that contains the electrostatic image developer set according to the present embodiment is preferably used.

[0138] The image forming apparatus according to this embodiment may be an image forming apparatus that contains the white toner included in the toner set according to this embodiment in a developing means, and also contains at least one color toner selected from yellow toner, magenta toner, cyan toner, and black toner in the developing means.

[0139] The recording medium on which the image forming apparatus (image forming method) according to the present embodiment records an image is not particularly limited, and any known recording medium can be used. Examples of the recording medium include resin films or sheets, paper, etc. Applications of the resin films or sheets include packages, labels, packaging materials, etc. , advertising media, overhead projector sheets, etc.

[0140] Examples of the resin film or sheet include polyolefin films or sheets such as polyethylene and polypropylene; polyester films or sheets such as polyethylene terephthalate and polybutylene terephthalate; polyamide films or sheets such as nylon; films or sheets of polycarbonate, polystyrene, modified polystyrene, polyvinyl chloride, polyvinyl alcohol, polylactic acid, etc. These films or sheets may be either unstretched films or sheets or uniaxially or biaxially stretched films or sheets. The resin film or sheet may be in the form of either a single layer or a multilayer. The resin film or sheet may be a film having a surface coating layer that assists toner fixation, or a film or sheet that has been subjected to corona treatment, ozone treatment, plasma treatment, flame treatment, glow discharge treatment, etc.

[0141] Examples of the lamination order of the recording medium, the color image, and the white image (concealing layer) include the following (a), (b), and (c). Stacking order (a): from the side closest to the viewer, a transparent recording medium / a colored image / a white image (hiding layer). Stacking order (b): from the side closest to the viewer, a colored image / a transparent recording medium / a white image (hiding layer). Stacking order (c): From the side closest to the viewer, a colored image / a white image (hiding layer) / a recording medium (whether or not it is transparent).

[0142] An example of an image forming apparatus according to the present embodiment will be described below, but the present invention is not limited to this. Note that only the main parts shown in the drawings will be described, and descriptions of the rest will be omitted.

[0143] FIG. 1 is a schematic diagram showing the configuration of an image forming apparatus according to the present embodiment, and shows a five-unit tandem type and intermediate transfer type image forming apparatus. The image forming apparatus shown in Fig. 1 includes first to fifth image forming units 10Y, 10M, 10C, 10K, and 10W (image forming means) of an electrophotographic type that output images of each color of yellow (Y), magenta (M), cyan (C), black (K), and white (W) based on color-separated image data. These image forming units (hereinafter sometimes simply referred to as "units") 10Y, 10M, 10C, 10K, and 10W are arranged in parallel at predetermined distances from each other in the horizontal direction. These units 10Y, 10M, 10C, 10K, and 10W may be process cartridges that are detachably attached to the image forming apparatus.

[0144] An intermediate transfer belt (an example of an intermediate transfer body) 20 is provided below each of the units 10Y, 10M, 10C, 10K, and 10W and extends through each of the units. The intermediate transfer belt 20 is provided wrapped around a drive roll 22, a support roll 23, and an opposing roll 24 that contact the inner surface of the intermediate transfer belt 20, and runs in a direction from the first unit 10Y to the fifth unit 10W. An intermediate transfer body cleaning device 21 is provided on the image bearing surface side of the intermediate transfer belt 20, facing the drive roll 22. The developing devices (examples of developing means) 4Y, 4M, 4C, 4K, and 4W of each unit 10Y, 10M, 10C, 10K, and 10W are supplied with yellow, magenta, cyan, black, and white toner contained in toner cartridges 8Y, 8M, 8C, 8K, and 8W, respectively.

[0145] Since the first to fifth units 10Y, 10M, 10C, 10K, and 10W have the same configuration, operation, and function, the following description will focus on the first unit 10Y, which forms a yellow image and is disposed upstream in the direction of travel of the intermediate transfer belt.

[0146] The first unit 10Y has a photoconductor 1Y that acts as an image carrier. Around the photoconductor 1Y, there are sequentially arranged a charging roll (an example of a charging means) 2Y that charges the surface of the photoconductor 1Y to a predetermined potential, an exposure device (an example of an electrostatic image forming means) 3Y that exposes the charged surface to a laser beam based on a color-separated image signal to form an electrostatic image, a developing device (an example of a developing means) 4Y that supplies toner to the electrostatic image to develop it, a primary transfer roll (an example of a primary transfer means) 5Y that transfers the developed toner image onto the intermediate transfer belt 20, and a photoconductor cleaning device (an example of a cleaning means) 6Y that removes toner remaining on the surface of the photoconductor 1Y after the primary transfer. The primary transfer roll 5Y is disposed inside the intermediate transfer belt 20, and is provided at a position facing the photoconductor 1Y. A bias power supply (not shown) that applies a primary transfer bias is connected to the primary transfer rolls 5Y, 5M, 5C, 5K, and 5W of each unit. Each bias power supply changes the value of the transfer bias applied to each primary transfer roll under the control of a control unit (not shown).

[0147] Hereinafter, the operation of forming a yellow image in first unit 10Y will be described. First, prior to operation, the surface of the photoconductor 1Y is charged to a potential of −600V to −800V by the charging roll 2Y. The photoconductor 1Y has a conductivity (for example, a volume resistivity of 1×10 at 20° C. -6The photosensitive layer is formed by laminating a photosensitive layer on a substrate having a resistivity of Ωcm or less. This photosensitive layer is usually highly resistive (the resistance of ordinary resins), but when irradiated with a laser beam, the resistivity of the portion irradiated with the laser beam changes. Therefore, the charged surface of the photosensitive member 1Y is irradiated with a laser beam from the exposure device 3Y in accordance with image data for yellow sent from a control unit (not shown). As a result, an electrostatic charge image of a yellow image pattern is formed on the surface of the photosensitive member 1Y.

[0148] An electrostatic image is an image formed on the surface of the photoconductor 1Y by electrostatic charging. The laser beam from the exposure device 3Y reduces the resistivity of the irradiated parts of the photosensitive layer, causing the charged charges on the surface of the photoconductor 1Y to flow, while the charges remain in the parts not irradiated by the laser beam. This is a so-called negative latent image. The electrostatic image formed on the photoconductor 1Y rotates to a predetermined developing position as the photoconductor 1Y travels. At this developing position, the electrostatic image on the photoconductor 1Y is developed into a toner image by the developing device 4Y and made visible.

[0149] The developing device 4Y contains an electrostatic image developer including at least yellow toner and a carrier, for example. The yellow toner is triboelectrically charged by being stirred inside the developing device 4Y, and is held on a developer roll (an example of a developer holder) with a charge of the same polarity (negative polarity) as the charge on the photoconductor 1Y. As the surface of the photoconductor 1Y passes through the developing device 4Y, the yellow toner electrostatically adheres to the discharged latent image portion on the surface of the photoconductor 1Y, and the latent image is developed with the yellow toner. The photoconductor 1Y on which the yellow toner image has been formed continues to travel at a predetermined speed, and the toner image developed on the photoconductor 1Y is transported to a predetermined primary transfer position.

[0150] When the yellow toner image on the photoconductor 1Y is transported to the primary transfer position, a primary transfer bias is applied to the primary transfer roll 5Y, and an electrostatic force from the photoconductor 1Y toward the primary transfer roll 5Y acts on the toner image, and the toner image on the photoconductor 1Y is transferred onto the intermediate transfer belt 20. The transfer bias applied at this time has a polarity (+) opposite to the polarity (-) of the toner, and is controlled to, for example, +10 μA by a control unit (not shown) in the first unit 10Y. On the other hand, the toner remaining on the photoconductor 1Y is removed and collected by the photoconductor cleaning device 6Y.

[0151] The primary transfer bias applied to the primary transfer rolls 5M, 5C, 5K, and 5W in the second unit 10M and subsequent units is also controlled in accordance with the first unit. In this manner, the intermediate transfer belt 20 onto which the yellow toner image has been transferred by the first unit 10Y is conveyed successively through the second to fifth units 10M, 10C, 10K, and 10W, where the toner images of each color are transferred and superimposed.

[0152] The intermediate transfer belt 20 onto which the five color toner images have been transferred in multiple layers through the first to fifth units reaches a secondary transfer section that is composed of the intermediate transfer belt 20, an opposing roll 24 that contacts the inner surface of the intermediate transfer belt, and a secondary transfer roll (an example of a secondary transfer means) 26 arranged on the image bearing surface side of the intermediate transfer belt 20. Meanwhile, a recording paper (an example of a recording medium) P is fed at a predetermined timing into the gap between the secondary transfer roll 26 and the intermediate transfer belt 20 via a supply mechanism, and a secondary transfer bias is applied to the opposing roll 24. The transfer bias applied at this time has a (-) polarity that is the same as the (-) polarity of the toner, and an electrostatic force from the intermediate transfer belt 20 toward the recording paper P acts on the toner image, and the toner image on the intermediate transfer belt 20 is transferred onto the recording paper P. The secondary transfer bias at this time is determined according to the resistance detected by a resistance detection means (not shown) that detects the resistance of the secondary transfer section, and is voltage-controlled.

[0153] Thereafter, the recording paper P is sent to a pressure contact portion (nip portion) of a pair of fixing rolls in a fixing device (one example of a fixing means) 28, where the toner image is fixed onto the recording paper P, forming a fixed image.

[0154] The recording paper P onto which the toner image is transferred can be, for example, plain paper used in electrophotographic copying machines, printers, etc. In addition to the recording paper P, other examples of the recording medium include overhead projector sheets and the like. To further improve the smoothness of the image surface after fixing, it is preferable that the surface of the recording paper P is also smooth. For example, coated paper in which the surface of ordinary paper is coated with a resin or the like, art paper for printing, etc. are preferably used.

[0155] After the color image has been fixed, the recording paper P is conveyed toward the discharge section, and the series of color image forming operations is completed.

[0156] <Process cartridge / toner cartridge set> The process cartridge according to this embodiment will be described. The process cartridge according to this embodiment is a process cartridge that is detachably attached to an image forming apparatus and includes a first developing means that contains a white electrostatic image developer from the electrostatic image developer set according to this embodiment, and a second developing means that contains a colored electrostatic image developer from the electrostatic image developer set according to this embodiment.

[0157] In addition, the process cartridge according to this embodiment is not limited to the above configuration, and may be configured to include a developing device and, as necessary, at least one other means selected from an image carrier, a charging means, an electrostatic image forming means, and a transfer means.

[0158] An example of a process cartridge according to the present embodiment will be described below, but the present invention is not limited to this example. Note that only the main parts shown in the drawings will be described, and descriptions of the rest will be omitted.

[0159] FIG. 2 is a schematic diagram showing the process cartridge according to the present embodiment. The process cartridge 200 shown in FIG. 2 is, for example, a housing 117 provided with a mounting rail 116 and an opening 118 for exposure, and includes a photoconductor 107 (an example of an image carrier), a charging roll 108 (an example of a charging means) provided around the photoconductor 107, a developing device 11, and a developing unit 12. The developing device 1 (an example of a developing means) and the photoconductor cleaning device 113 (an example of a cleaning means) are integrally combined and held to form a cartridge. In FIG. 2, 109 denotes an exposure device (an example of an electrostatic image forming means), 112 denotes a transfer device (an example of a transfer means), 115 denotes a fixing device (an example of a fixing means), and 300 denotes recording paper (an example of a recording medium).

[0160] Next, the toner cartridge set according to this embodiment will be described. The toner cartridge set according to the present embodiment is a toner cartridge set including a white toner cartridge that contains the white toner contained in the toner set according to the present embodiment and is detachably attached to the image forming apparatus, and a color toner cartridge that contains the color toner contained in the toner set according to the present embodiment and is detachably attached to the image forming apparatus. The toner cartridge set contains replenishment toner to be supplied to a developing means provided in the image forming apparatus.

[0161] 2 is an image forming apparatus having a configuration in which toner cartridges 8Y, 8M, 8C, 8K, and 8W are detachably attached, and developing devices 4Y, 4M, 4C, 4K, and 4W are connected to toner cartridges corresponding to the respective developing devices (colors) by toner supply pipes (not shown). When the toner contained in a toner cartridge becomes low, the toner cartridge is replaced. EXAMPLES

[0162] Hereinafter, the embodiments of the present invention will be described in detail with reference to examples, but the embodiments of the present invention are not limited to these examples. In the following description, unless otherwise specified, "parts" and "%" are based on mass.

[0163] <Preparation of various dispersions> (Synthesis of amorphous polyester resin (A)) Terephthalic acid: 68 parts Fumaric acid: 32 parts Ethylene glycol: 42 parts 1,5-Pentanediol: 47 parts The above materials were placed in a flask equipped with a stirrer, a nitrogen inlet tube, a temperature sensor, and a distillation column, and the temperature was raised to 220°C over 1 hour under a nitrogen gas flow, and 1 part of titanium tetraethoxide was added for a total of 100 parts of the above materials. The temperature was raised to 240°C over 0.5 hours while distilling off the generated water, and the dehydration condensation reaction was continued at 240°C for 1 hour, after which the reaction product was cooled. In this way, an amorphous polyester resin (A) with a weight average molecular weight of 97,000 and a glass transition temperature of 60°C was obtained.

[0164] (Preparation of amorphous polyester resin particle dispersion (A1)) In a vessel equipped with a temperature control means and a nitrogen substitution means, 40 parts of ethyl acetate and 25 parts of 2-butanol were added to prepare a mixed solvent, and then 100 parts of amorphous polyester resin (A) were gradually added and dissolved, and 10% aqueous ammonia solution (equivalent to 3 times the amount by mole relative to the acid value of the resin) was added thereto and stirred for 30 minutes. Next, the inside of the vessel was substituted with dry nitrogen, the temperature was kept at 40°C, and 400 parts of ion-exchanged water was dropped into the mixed liquid while stirring, to perform emulsification. After the dropwise addition, the emulsion was returned to 25°C, and a resin particle dispersion in which resin particles with a volume average particle size of 195 nm were dispersed was obtained. Ion-exchanged water was added to this resin particle dispersion to adjust the solid content to 20%, and an amorphous polyester resin particle dispersion (A1) was obtained.

[0165] (Preparation of Crystalline Polyester Resin Particle Dispersion (B1)) 1,10-Decanedicarboxylic acid: 260 parts 1,6-Hexanediol: 167 parts Dibutyltin oxide (catalyst): 0.3 parts The above materials were placed in a heated and dried three-necked flask, the air in the three-necked flask was replaced with nitrogen gas to create an inert atmosphere, and the mixture was stirred and refluxed at 180°C for 5 hours by mechanical stirring. Next, the temperature was gradually raised to 230°C under reduced pressure and stirred for 2 hours, and when the mixture became viscous, it was air-cooled to stop the reaction. Thus, a crystalline polyester resin with a weight average molecular weight of 12500 and a melting temperature of 73°C was obtained. 90 parts of the crystalline polyester resin, 1.8 parts of anionic surfactant (TaycaPower, manufactured by Tayca Co., Ltd., solid content 12%, sodium dodecylbenzenesulfonate) and 210 parts of ion-exchanged water were mixed, heated to 120°C, and dispersed using a homogenizer (Ultra Turrax T50 manufactured by IKA Co., Ltd.), and then dispersed for 1 hour using a pressure discharge type Gaulin homogenizer to obtain a resin particle dispersion in which resin particles with a volume average particle size of 195 nm were dispersed. Ion-exchanged water was added to this resin particle dispersion to adjust the solid content to 20%, thereby obtaining a crystalline polyester resin particle dispersion (B1).

[0166] (Preparation of styrene acrylic resin particle dispersion (S1)) Styrene: 375 parts n-Butyl acrylate: 25 parts Acrylic acid: 2 parts Dodecanethiol: 24 parts Carbon tetrabromide: 4 parts The mixture obtained by mixing and dissolving the above materials was dispersed and emulsified in a flask in a surfactant solution in which 6 parts of a nonionic surfactant (manufactured by Sanyo Chemical Industries, Nonipol 400) and 10 parts of an anionic surfactant (manufactured by TaycaPower, Tayca Co., Ltd., solid content 12%, sodium dodecylbenzenesulfonate) were dissolved in 550 parts of ion-exchanged water. Next, an aqueous solution in which 4 parts of ammonium persulfate were dissolved in 50 parts of ion-exchanged water was added over a period of 20 minutes while stirring the flask. Next, after nitrogen replacement, the flask was heated in an oil bath while stirring the contents until the temperature reached 70°C, and the temperature was maintained at 70°C for 5 hours to continue emulsion polymerization. Thus, a resin particle dispersion in which resin particles having a volume average particle size of 150 nm were dispersed was obtained. Ion-exchanged water was added to this resin particle dispersion to adjust the solid content to 20%, and a styrene acrylic resin particle dispersion (S1) was obtained.

[0167] (Preparation of colorant dispersion (Cy1)) CI Pigment Blue 15:3 (Dainichi Seika Chemicals): 70 parts Anionic surfactant (Neogen RK, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.): 1 part Ion-exchanged water: 200 parts The above materials were mixed and dispersed for 10 minutes using a homogenizer (Ultra Turrax T50 manufactured by IKA Corporation). Ion-exchanged water was added so that the solid content in the dispersion was 20%, and a colorant dispersion (Cy1) in which colorant particles with a volume average particle size of 190 nm were dispersed was obtained.

[0168] (Preparation of styrene acrylic modified polyester resin particle dispersion (SPE1) The inside of a four-neck flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer, and a thermocouple was replaced with nitrogen, and 5,670 parts of polyoxypropylene (2.2)-2,2-bis (4-hydroxyphenyl) propane, 585 parts of polyoxyethylene (2.0)-2,2-bis (4-hydroxyphenyl) propane, 2,450 parts of terephthalic acid, and 44 parts of tin (II) di (2-ethylhexanoate) were added. The mixture was heated to 235 ° C. under a nitrogen atmosphere while stirring, and maintained for 5 hours. The pressure in the flask was then further reduced and maintained at 8.0 kPa for 1 hour. After returning to atmospheric pressure, the mixture was cooled to 190 ° C., 42 parts of fumaric acid and 207 parts of trimellitic acid were added, and the mixture was maintained at a temperature of 190 ° C. for 2 hours, and then heated to 210 ° C. over 2 hours. The pressure in the flask was further reduced and maintained at 8.0 kPa for 4 hours to obtain an amorphous polyester resin A (polyester segment). Next, 800 parts of amorphous polyester resin A was added to a four-neck flask equipped with a cooling tube, a stirrer, and a thermocouple, and stirring was performed at a stirring speed of 200 rpm under a nitrogen atmosphere. After that, 100 parts of styrene, 82 parts of ethyl acrylate, 16 parts of acrylic acid, 2 parts of 1,10-decanediol diacrylate, and 1.00 parts of toluene were added as addition polymerizable monomers, and mixed for another 30 minutes. Furthermore, 6 parts of polyoxyethylene alkyl ether (nonionic surfactant, trade name: Emulgen 430, manufactured by Kao Corporation), 40 parts of a 15% aqueous sodium dodecylbenzenesulfonate solution (anionic surfactant, trade name: Neopelex G-15, manufactured by Kao Corporation) and 233 parts of 5% potassium hydroxide were added, and the mixture was heated to 95°C with stirring to melt, and mixed at 95°C for 2 hours to obtain a resin mixture solution. Next, while stirring the resin mixture solution, 1,145 parts of deionized water was added dropwise at a rate of 6 parts / min to obtain an emulsion. Next, the obtained emulsion was cooled to 25°C, passed through a 200-mesh wire screen, and deionized water was added to adjust the solid content to 30%, thereby obtaining a styrene-acrylic modified polyester resin particle dispersion (SPE1). The "mass ratio of the styrene-acrylic resin segment to the polyester resin segment (styrene-acrylic resin segment / polyester resin segment)" of the synthesized styrene-acrylic modified polyester resin was 20 / 80.

[0169] (Preparation of release agent particle dispersion (W1)) Ester wax (Nippon Oil & Fats Co., Ltd., WEP-8, melting temperature 79°C): 100 parts Anionic surfactant: 1 part (TaycaPower, manufactured by Tayca Corporation, sodium dodecylbenzenesulfonate) Ion-exchanged water: 350 parts The above materials were mixed and heated to 100°C, dispersed using a homogenizer (IKA Ultra Turrax T50), and then dispersed using a pressure discharge Gaulin homogenizer to obtain a release agent particle dispersion in which release agent particles with a volume average particle size of 1000 nm were dispersed. Ion-exchanged water was added to this release agent particle dispersion to adjust the solid content to 20%, and this was used as release agent particle dispersion (W1).

[0170] <Production of colored toner> (Preparation of Cyan Toner (CT1)) -First agglomerated particle formation process- Ion-exchanged water: 200 parts Colorant dispersion (Cy1): 15 parts Release agent particle dispersion (W1): 10 parts Styrene acrylic resin particle dispersion (S1): 40 parts Crystalline polyester resin particle dispersion (B1): 10 parts Amorphous polyester resin particle dispersion (A1): 230 parts

[0171] The above materials were placed in a round stainless steel flask, and 0.1N (0.1mol / L) nitric acid was added to adjust the pH to 3.5, after which an aqueous magnesium chloride solution in which 6 parts of magnesium chloride were dissolved in 30 parts of ion-exchanged water was added. The materials were dispersed at 30°C using a homogenizer (IKA Ultra Turrax T50), and then heated to 45°C in a heating oil bath and maintained until the volume average particle size reached 4.5μm.

[0172] -Second agglomerated particle formation process- Then, the mixture was held for 30 minutes. Every 30 minutes, 5 parts of the styrene acrylic resin particle dispersion (S1) was added four times in total. After that, while continuing to stir, the pH was adjusted to 9.0 using 1N aqueous sodium hydroxide solution.

[0173] -Fusion / unification process- Next, while continuing stirring, the temperature was increased to 85°C at a rate of 0.05°C / min, and after being held at 85°C for 3 hours, it was cooled to 30°C at a rate of 15°C / min (first cooling). Next, it was heated to 85°C at a rate of 0.2°C / min (reheating), held for 30 minutes, and then cooled to 30°C at a rate of 0.5°C / min (second cooling). Next, the solid content was filtered off, washed with ion-exchanged water, and dried to obtain cyan toner particles (CT1) having a volume average particle size of 4.7 μm.

[0174] -External addition of external additives- 100 parts of the cyan toner particles (CT1) and 1.5 parts of hydrophobic silica (RY50, manufactured by Nippon Aerosil Co., Ltd.) were mixed and mixed for 30 seconds at a rotation speed of 10,000 rpm using a sample mill. The mixture was sieved using a vibrating sieve with an opening of 45 μm to obtain a cyan toner (CT1).

[0175] (Preparation of Cyan Toner (CT2)) Cyan toner (CT2) was obtained in the same manner as for cyan toner (CT1), except that in the first aggregate particle formation step, the styrene acrylic resin particle dispersion (S1) was 160 parts and the amorphous polyester resin particle dispersion (A1) was 110 parts.

[0176] (Preparation of Cyan Toner (CT3)) A cyan toner (CT3) was obtained in the same manner as for the cyan toner (CT1), except that in the first aggregate particle forming step, the styrene acrylic resin particle dispersion (S1) was 80 parts and the amorphous polyester resin particle dispersion (A1) was 190 parts.

[0177] (Preparation of Cyan Toner (CT4)) Cyan toner (CT4) was obtained in the same manner as for cyan toner (CT1), except that in the first aggregate particle formation step, the styrene acrylic resin particle dispersion (S1) was 25 parts and the amorphous polyester resin particle dispersion (A1) was 250 parts.

[0178] (Preparation of Cyan Toner (CT5)) Cyan toner (CT5) was obtained in the same manner as for cyan toner (CT1), except that in the first aggregate particle formation step, the styrene acrylic resin particle dispersion (S1) was 5 parts and the amorphous polyester resin particle dispersion (A1) was 265 parts. (Preparation of Cyan Toner (CT6)) Cyan toner (CT6) was obtained in the same manner as for cyan toner (CT1), except that in the first aggregate particle formation step, the styrene acrylic resin particle dispersion (S1) was 17 parts and the amorphous polyester resin particle dispersion (A1) was 100 parts.

[0179] (Preparation of Cyan Toner (CT7)) Cyan toner (CT7) was obtained in the same manner as for cyan toner (CT1), except that in the first aggregate particle formation step, the amount of styrene acrylic resin particle dispersion (S1) was 0 part and the amount of amorphous polyester resin particle dispersion (A1) was 270 parts.

[0180] (Preparation of Cyan Toner (CT8)) Cyan toner (CT8) was obtained in the same manner as cyan toner (CT1), except that in the first aggregate particle formation step, 270 parts of styrene acrylic modified polyester resin particle dispersion (SPE1) was used instead of the styrene acrylic resin particle dispersion (S1) and the amorphous polyester resin particle dispersion (A1).

[0181] (Preparation of Cyan Toner (CT9)) Cyan toner (CT9) was obtained in the same manner as cyan toner (CT1), except that in the first aggregated particle formation process, the styrene acrylic resin particle dispersion (S1) was 0 part, and the amorphous polyester resin particle dispersion (A1) was 270 parts, and in the second aggregated particle formation process, the styrene acrylic resin particle dispersion (S1) was replaced with the amorphous polyester resin particle dispersion (A1).

[0182] <Preparation of white colorant> (Preparation of titanium oxide particles (T1)) 0.15 mol of glycerin was added to 100 mL of 1 mol / L titanium tetrachloride aqueous solution, heated at 90°C for 4 hours, and then filtered. The obtained white powder was dispersed in 100 mL of ion-exchanged water, 0.4 mol of hydrochloric acid was added, and heated again at 90°C for 3 hours. The pH was adjusted to 7 with sodium hydroxide, then filtered, washed with water, and dried at 105°C for 12 hours to obtain hydrous titanium dioxide particles (1). 100 parts of hydrous titanium dioxide particles (1) were mixed with 0.25 parts of Al2O3, 0.1 parts of aluminum sulfate, 1.2 parts of K2O, and 0.01 parts of P2O5, and calcined at 950°C for 2 hours to obtain titanium oxide particles (T1) with a number-average particle size Dcc of 500 nm.

[0183] (Preparation of titanium oxide particles (T2)) Titanium oxide particles (T2) having a number average particle size Dcc of 220 nm were obtained in the same manner as titanium oxide particles (T1), except that the amount of P2O5: was 0.05 parts and the firing temperature was 930°C.

[0184] (Preparation of titanium oxide particles (T3)) Titanium oxide particles (T3) having a number average particle size of 155 nm were obtained in the same manner as titanium oxide particles (T1), except that the amount of P2O5: was 0.1 parts, the amount of K2O was 0.5 parts, and the firing temperature was 920°C.

[0185] (Preparation of titanium oxide particles (T4)) Titanium oxide particles (T4) having a number average particle size Dcc of 570 nm were obtained in the same manner as titanium oxide particles (T1), except that the amount of P2O5 was 0.005 parts, the amount of K2O was 1.2 parts, the firing temperature was 970°C, and the firing time was 3 hours.

[0186] (White colorant (MT1)) 30 parts of titanium oxide particles (T1) and 70 parts of titanium oxide particles (T2) were mixed with 200 parts of ion-exchanged water adjusted to pH 4 with 0.1 N hydrogen chloride solution, and the mixture was dispersed overnight in a ball mill. The mixture was then left to stand, the supernatant was removed, and the mixture was dried for 12 hours in a vacuum freeze dryer, then crushed in a jet mill and sieved to remove coarse powder. In this way, an oxide white colorant (MT1) with a number-average particle size Dcc of 280 nm was obtained.

[0187] (Preparation of white colorants (MT2) to (MT16)) Titanium oxide particles (T1): the amount A (parts) shown in Table 2, titanium oxide particles (T2): the amount B (parts) shown in Table 2, and titanium oxide particles (T3): the amount C (parts) shown in Table 2 were mixed with 200 parts of ion-exchanged water adjusted to pH 4 with a 0.1 N hydrogen chloride solution, and the mixture was dispersed overnight in a ball mill. The mixture was then left to stand, the supernatant was removed, and the mixture was dried for 12 hours in a vacuum freeze dryer, then crushed in a jet mill and sieved to remove coarse powder. In this way, white colorants (MT2) to (MT16) with number-average particle diameters Dcc shown in Table 2 were obtained.

[0188] (Preparation of white colorant (MT17)) 100 parts of titanium oxide particles (T4) were mixed with 200 parts of ion-exchanged water adjusted to pH 4 with 0.1 N hydrogen chloride solution, and the mixture was dispersed overnight in a ball mill. The mixture was then left to stand to remove the supernatant, dried in a vacuum freeze dryer for 12 hours, then crushed in a jet mill, and sieved to remove coarse powder. In this way, a white colorant (MT17) with a number average particle size Dcc of 525 nm was obtained.

[0189] <Preparation of White Toner (WT1)> -Preparation of toner particle forming materials- As the toner particle forming material, the following materials were prepared. Styrene acrylic resin (resin polymerized with styrene and butyl acrylate under cumene reflux): 10 parts Polyester resin (polyester resin synthesized using a tin catalyst, mainly composed of bisphenol A propylene oxide 2-mol adduct / ethylene oxide 2-mol adduct, terephthalic acid, and trimellitic acid): 47.5 parts White colorant (MT1): 80 parts Release agent (polypropylene; Mitsui Chemicals, Inc., Mitsui HI-WAX NP055): 5 parts

[0190] -Kneading process- The above toner forming materials were mixed in a Henschel mixer, and then kneaded under the following conditions in a twin-screw extruder (that is, a continuous kneader) shown in Figure 3. The screw rotation speed was 500 rpm. Feed section (blocks 12A and 12B) set temperature: 20℃ Kneading section 1 kneading temperature setting (blocks 12C to 12E): 100℃ Kneading section 2 kneading temperature setting (blocks 12F to 12J): 110℃ Amount of aqueous medium (distilled water) added (per 100 parts of raw material supply): 1.5 parts In the kneading under the above conditions, the temperature of the kneaded mixture at the outlet (outlet 18) of the screw extruder 11 was 120°C.

[0191] The obtained kneaded material was rapidly cooled using a rolling roll with -5°C brine passing through it and a slab-sandwiched cooling belt cooled with 2°C cold water, and then crushed using a hammer mill. The rapid cooling rate was confirmed by changing the speed of the cooling belt, and the average temperature drop rate was 10°C / sec.

[0192] The kneaded material obtained in the mixing process was then pulverized in a pulverizer (AFG400) with a built-in coarse particle classifier to obtain pulverized particles, which were then classified in an inertial classifier to remove fine and coarse particles, obtaining white toner particles (WT1) with a volume average particle size of 6.0 μm.

[0193] -External addition of external additives- To the obtained white toner particles (W1), hydrophobic silica (RY50 manufactured by Nippon Aerosil Co., Ltd.) and 1.2 parts of hexamethyldisilazane-treated spherical silica having an average particle diameter of 130 nm were added, and the mixture was mixed (externally added) for 10 minutes using a Henschel mixer. After that, the mixture was sieved to 45 μm using a wind sieve (Hivolter) to obtain white toner (WT1).

[0194] (Preparation of White Toner (WT2) to (WT16)) Except for changing the type and amount of the white colorant to type and amount added D shown in Table 2, toners (WT2) to (WT16) were obtained in the same manner as for white toner (WT1).

[0195] (Preparation of white toner (WT17)) A toner (WT17) was obtained in the same manner as for the white toner (WT1), except that the white colorant (MT1) was changed to a white colorant (MT17).

[0196] <Examples 1 to 24 and Comparative Examples 1 to 7> A toner set of a cyan toner and a white toner shown in Table 1 was used as the toner set for each example. After the toner of each example was set, the cyan toner and the carrier (CA) obtained by the method described below were placed in a V blender in a mass ratio (toner / carrier) of 5 / 95 and stirred for 20 minutes to obtain the cyan developer of each example. On the other hand, after the toner setting of each example, the white toner and the carrier (CB) obtained by the method described below were placed in a V blender in a mass ratio (toner / carrier) of 8 / 92 and stirred for 20 minutes to obtain the white developer of each example. The obtained cyan developer and white developer were used as developer sets for each example.

[0197] -Creation of Carrier (CA)- After 500 parts of spherical magnetite powder particles (volume average particle diameter 0.55 μm) were stirred with a Henschel mixer, 5 parts of a titanate-based coupling agent were added, and the mixture was heated to 100 ° C and stirred for 30 minutes. Next, 6.25 parts of phenol, 9.25 parts of 35% formalin, 500 parts of magnetite particles treated with a titanate-based coupling agent, 6.25 parts of 25% ammonia water, and 425 parts of water were added to a four-neck flask and stirred, and reacted at 85 ° C for 120 minutes while stirring. Next, the mixture was cooled to 25 ° C, 500 parts of water were added, and the supernatant liquid was removed and the precipitate was washed with water. The washed precipitate was heated and dried under reduced pressure to obtain a carrier (CA) with an average particle size of 35 μm.

[0198] -Creating the carrier (CB)- A mixture of 2.0 parts of cyclohexyl methacrylate resin (weight average molecular weight: 150,000), 0.6 parts of carbon black (VXC72), and 0.3 parts by mass of melamine beads (Eposter S) dissolved in 10 parts of toluene was coated using a kneader to obtain a carrier (CB) for 100 parts of ferrite cores having a volume average particle diameter of 35 μm.

[0199] <Evaluation> The developer sets of each example were used to carry out the following evaluations. First, the developer from each example developer set was placed in a production printer, the "Iridesse Production Press Modified Machine (FUJIFILM Business Innovation Co., Ltd.)" as an image forming device. Then, using this image forming apparatus, the following evaluations were carried out.

[0200] (Color development evaluation of colored images) Under normal temperature and humidity (25°C, 50% RH) conditions, A4 size black paper (76.7 g / m 2 , Marubeni Forest Links Co., Ltd.) on paper with a white toner of 6 g / m 2 , cyan toner is 4g / m 2A white image and a cyan image were formed in this order from the side closest to the paper, with the amount of toner applied being 1 inch square (2.54 cm x 2.54 cm). And the brightness of the image (L * The color development of the colored image was evaluated based on the following evaluation criteria. -Evaluation criteria- A: Lightness 70 or more A-: Lightness is 68 or more and less than 70 B+: Lightness is between 65 and 68 B: Lightness is 62 or more and less than 65 C: Lightness is between 56 and 62 D: Lightness 55 or less

[0201] (Bending resistance evaluation) The image obtained in the evaluation of the color development of the colored image was folded and a crease evaluation was performed to judge the degree of peeling of the image. Specifically, the paper on which an image was formed was folded once, unfolded, and the folded image was wiped with cotton. The width of the peeled (whitened) image was taken as the crease value and evaluated according to the following criteria. -Evaluation criteria- A: Crease value is 20μm or less A-: Crease value is over 20μm and 35μm or less B+: Crease value is over 35μm and 50μm or less B: Crease value is more than 50 μm and less than 80 μm C: Crease value is over 80μm and 160μm or less D: Crease value exceeds 160 μm

[0202] Table 1 shows the following characteristics of the white toner and color toner (cyan toner in this embodiment). Vinyl resin content relative to colored toner particles: mass% (referred to as "StAc ratio CS" in Table 1) Polyester resin content in colored toner particles: mass% (referred to as "PES ratio CP" in Table 1) Mass ratio C of polyester resin to vinyl resin in colored toner particles (referred to as "PES / StAc ratio C") Vinyl resin content in white toner particles: mass% (referred to as "StAc ratio WS" in Table 1) Polyester resin content in white toner particles: mass% (referred to as "PES ratio WP" in Table 1) Mass ratio C of polyester resin to vinyl resin in white toner particles (referred to as "PES / StAc ratio W")

[0203] The area ratio of the white colorant when observing the cross section of a white toner particle (referred to as "colorant area ratio" in the table) Number average particle diameter of the white colorant when observing the cross section of a white toner particle (referred to as "particle diameter of colorant" in the table) The ratio of white colorants with a particle size of 100 nm or less to all white colorants when observing the cross section of a white toner particle (indicated as "Ratio of colorants with a particle size of 100 nm or less" in the table) Content of white colorant in white toner particles: mass% (referred to as "colorant amount" in the table)

[0204] [Table 1-1]

[0205] [Table 1-2]

[0206] [Table 2]

[0207] From the above results, it can be seen that in this embodiment, the color development of the colored image is higher than that of the comparative example, and the crease value is smaller in the evaluation of the folding resistance of the image, so that the color development of the image having a colored image on a white image is higher and peeling of the image when folded is suppressed.

[0208] The present embodiment includes the following aspects. (((1))) a white toner having white toner particles including a polyester resin and a white colorant; a non-white color toner having color toner particles including a vinyl resin, a polyester resin, and a color colorant; having a mass ratio C of the polyester resin to the vinyl resin in the color toner particles is 0.7 or more and 10 or less; A toner set for developing electrostatic images, wherein, when a cross section of the white toner particle is observed, the area ratio of the white colorant is 10% or more and 50% or less, and the number average particle size of the white colorant is 0.23 μm or more and 0.45 μm or less. (((2))) The toner set for developing electrostatic images according to (((1))), wherein a mass ratio C of the polyester resin to the vinyl resin in the color toner particles is 2 or more and 6 or less. (((3))) The toner set for developing electrostatic images according to (((1))) or (((2))), wherein, when a cross section of the white toner particle is observed, an area ratio of the white colorant is 20% or more and 50% or less, and the number average particle diameter of the white colorant is 0.23 μm or more and 0.30 μm or less. (((4))) The toner set for developing electrostatic images according to any one of ((1))) to (((3))), wherein the white toner particles contain a vinyl resin. (((5))) The toner set for developing electrostatic images according to (((4))), wherein a mass ratio W of the polyester resin to the vinyl resin in the white toner particles and a mass ratio C of the polyester resin to the vinyl resin in the color toner particles satisfy -0.6≦WC≦5.6. (((6))) The toner set for developing electrostatic images according to ((5))), wherein a mass ratio W of the polyester resin to the vinyl resin in the white toner particles and a mass ratio C of the polyester resin to the vinyl resin in the color toner particles satisfy 0≦WC≦4. (((7))) The toner set for developing electrostatic images according to any one of (((1))) to (((6))), wherein, when a cross section of the white toner particle is observed, a ratio of white colorants having a particle size of 100 nm or less to all white colorants is 30% by number or less. (((8))) The toner set for developing electrostatic images according to (((7))), wherein, when a cross section of the white toner particles is observed, the proportion of white colorants having a particle size of 100 nm or less to all the white colorants is 20% by number or less. (((9))) A white electrostatic image developer containing the white toner in the toner set for developing electrostatic images according to any one of (((1))) to (((8))), A color electrostatic image developer containing the color toner in the toner set for developing an electrostatic image according to any one of (((1))) to (((8))), an electrostatic image developer set comprising: (((10))) a white toner cartridge that contains the white toner contained in the toner set for developing electrostatic images according to any one of (((1))) to (((8))) and is detachably attached to an image forming apparatus; a color toner cartridge that contains the color toner contained in the toner set for developing an electrostatic image according to any one of (((1))) to (((8))) and is detachably attached to an image forming apparatus; Toner cartridge set including: (((11))) a first developing means containing the white electrostatic image developer contained in the electrostatic image developer set according to (((9))); a second developing means containing the color electrostatic image developer contained in the electrostatic image developer set according to (((9))); Equipped with A process cartridge that is detachably attached to an image forming apparatus. (((12))) a first image forming means that includes a first developing means that contains the white electrostatic image developer included in the electrostatic image developer set described in (((9))) and forms a white image using the white toner; a second image forming means for forming a color image using the color toner, the second image forming means including a second developing means containing the color electrostatic image developer included in the electrostatic image developer set described in (((9))), a transfer means for transferring the white image and the color image onto a surface of a recording medium; a fixing means for fixing the white image and the color image transferred onto the surface of the recording medium; An image forming apparatus comprising: (((13))) A first image forming step of forming a white image using the white toner contained in the toner set for developing electrostatic images according to any one of (((1))) to (8)); A second image forming step of forming a color image using the color toner contained in the toner set for developing an electrostatic image according to any one of (((1))) to (((8))); a transfer step of transferring the white image and the color image onto a surface of a recording medium; a fixing step of fixing the white image and the color image transferred onto the surface of the recording medium; The image forming method according to claim 1,

[0209] The advantages of the above aspect are as follows. According to the invention related to (((1))), there is provided a toner set for developing electrostatic images, which comprises a white toner having white toner particles containing a polyester resin and a white colorant, and a non-white color toner having colored toner particles containing a vinyl resin, a polyester resin, and a colored colorant, and which has a mass ratio C of the polyester resin to the vinyl resin in the colored toner particles that is less than 0.7 or exceeds 10, and when a cross-section of the colored toner particles is observed, the area ratio of the white colorant is less than 10% or exceeds 50%, or the number average particle size of the white colorant is less than 0.23 μm or exceeds 0.45 μm, and which has higher color development of an image having a colored image on a white image and suppresses peeling of the image when folded, compared to a toner set for developing electrostatic images in which the mass ratio C of the polyester resin to the vinyl resin in the colored toner particles is less than 0.7 or exceeds 10, and

[0210] According to the invention related to (((2))), there is provided a toner set for developing electrostatic images, which has high color development for an image having a color image on a white image and suppresses peeling of the image when folded, compared to when the mass ratio C of the polyester resin to the vinyl resin in the color toner particles is less than 2 or exceeds 6. According to the invention related to (((3))), there is provided a toner set for developing electrostatic images, which, when a cross section of a color toner particle is observed, has higher color development in an image having a colored image on a white image and is less susceptible to peeling of the image when folded, as compared with a case in which the area ratio of the white colorant is less than 20% or exceeds 50%, or the number average particle size of the white colorant is less than 0.23 μm or exceeds 0.30 μm. According to the invention related to (((4))), there is provided a toner set for developing electrostatic images, which has high color development for an image having a colored image on a white image and suppresses peeling of the image when folded, compared to a case in which the white toner particles contain only a polyester resin as a binder resin. According to the invention related to (((5))), there is provided a toner set for developing electrostatic images, which has higher color development in an image having a color image on a white image and suppresses peeling of the image when folded, compared to a case in which the relationship between the mass ratio W of the polyester resin to the vinyl resin in the white toner particles and the mass ratio C of the polyester resin to the vinyl resin in the color toner particles does not satisfy −0.6≦WC≦5.6. According to the invention related to (((6))), there is provided a toner set for developing electrostatic images, which has higher color development in an image having a color image on a white image and suppresses peeling of the image when folded, compared to a case in which the relationship between the mass ratio W of the polyester resin to the vinyl resin in the white toner particles and the mass ratio C of the polyester resin to the vinyl resin in the color toner particles does not satisfy 0≦WC≦4. According to the invention related to (((7))), there is provided a toner set for developing electrostatic images which, when a cross section of a white toner particle is observed, has higher color development in an image having a colored image on a white image, and which suppresses peeling of the image when folded, compared to a case in which the ratio of white colorants having a particle size of 100 nm or less to all white colorants exceeds 30% by number. According to the invention related to (((8))), there is provided a toner set for developing electrostatic images which, when a cross section of a white toner particle is observed, has higher color development in an image having a colored image on a white image, and which suppresses peeling of the image when folded, compared to a case in which the ratio of white colorants having a particle size of 100 nm or less to all white colorants exceeds 20% by number.

[0211] According to the invention pertaining to (((9))), (((10))), (((11))), (((12))), or (((13))), there is provided an electrostatic image developer set, a toner cartridge set, a process cartridge, an image forming apparatus, or an image forming method, which comprises a white toner having white toner particles containing a polyester resin and a white colorant, and a non-white colored toner having colored toner particles containing a vinyl resin, a polyester resin, and a colored colorant, and which has a mass ratio C of the polyester resin to the vinyl resin in the colored toner particles that is less than 0.7 or exceeds 10, and when a cross section of the colored toner particles is observed, the area ratio of the white colorant is less than 10% or exceeds 50%, or the number average particle diameter of the white colorant is less than 0.23 μm or exceeds 0.45 μm, and which has high color development of an image having a colored image on a white image and suppresses peeling of the image when folded, compared to the case where an electrostatic image developing toner set is applied. [Explanation of symbols]

[0212] 1Y, 1M, 1C, 1K, 1W Photoconductor (an example of an image carrier) 2Y, 2M, 2C, 2K, 2W Charging roll (an example of charging means) 3Y, 3M, 3C, 3K, 3W exposure device (an example of electrostatic image forming means) 4Y, 4M, 4C, 4K, 4W developing device (an example of developing means) 5Y, 5M, 5C, 5K, 5W Primary transfer roll (an example of a primary transfer means) 6Y, 6M, 6C, 6K, 6W: Photoconductor cleaning device (an example of a cleaning means) 8Y, 8M, 8C, 8K, 8W toner cartridges 10Y, 10M, 10C, 10K, 10W Image forming unit 20 Intermediate transfer belt (an example of an intermediate transfer body) 21 Intermediate transfer body cleaning device 22 Driving Roll 23 Support roll 24 Opposing Roll 26 Secondary transfer roll (an example of a secondary transfer means) 28 Fixing device (an example of fixing means) P Resin sheet (an example of a recording medium)

[0213] 107 Photoconductor (an example of an image carrier) 108 Charging roll (an example of charging means) 109 Exposure device (an example of electrostatic image forming means) 111 Developing device (an example of developing means) 112 Transfer device (an example of a transfer means) 113 Photoconductor cleaning device (an example of a cleaning means) 115 Fixing device (an example of fixing means) 116 Mounting Rail 117 Cabinet 118 Exposure Aperture 200 Process Cartridge 300 Resin sheet (an example of a recording medium)

Claims

1. a white toner having white toner particles including a polyester resin and a white colorant; a non-white color toner having color toner particles including a vinyl resin, a polyester resin, and a color colorant; having a mass ratio C of the polyester resin to the vinyl resin in the color toner particles is 0.7 or more and 10 or less; a toner set for developing an electrostatic image, wherein, when a cross section of the white toner particle is observed, an area ratio of the white colorant is 10% or more and 50% or less, and the number average particle diameter of the white colorant is 0.23 μm or more and 0.45 μm or less.

2. 2. The toner set for developing electrostatic images according to claim 1, wherein a mass ratio C of the polyester resin to the vinyl resin in the color toner particles is 2 or more and 6 or less.

3. 2. The toner set for developing electrostatic images according to claim 1, wherein, when a cross section of the white toner particle is observed, an area ratio of the white colorant is 20% or more and 50% or less, and a number average particle diameter of the white colorant is 0.23 μm or more and 0.30 μm or less.

4. 2. The toner set for developing electrostatic images according to claim 1, wherein the white toner particles contain a vinyl resin.

5. 5. The toner set for developing electrostatic images according to claim 4, wherein a mass ratio W of the polyester resin to the vinyl resin in the white toner particles and a mass ratio C of the polyester resin to the vinyl resin in the color toner particles satisfy a relationship of -0.6≦W−C≦5.

6.

6. 6. The toner set for developing electrostatic images according to claim 5, wherein a mass ratio W of the polyester resin to the vinyl resin in the white toner particles and a mass ratio C of the polyester resin to the vinyl resin in the color toner particles satisfy a relationship of 0≦W−C≦4.

7. 2. The toner set for developing electrostatic images according to claim 1, wherein, when a cross section of the white toner particles is observed, the ratio of white colorants having a particle size of 100 nm or less to all the white colorants is 30% by number or less.

8. 8. The toner set for developing electrostatic images according to claim 7, wherein, when a cross section of the white toner particles is observed, the ratio of white colorants having a particle size of 100 nm or less to all the white colorants is 20% by number or less.

9. A white electrostatic image developer containing the white toner contained in the toner set for developing electrostatic images according to any one of claims 1 to 8; A color electrostatic image developer containing the color toner contained in the toner set for developing an electrostatic image according to any one of claims 1 to 8; an electrostatic image developer set comprising:

10. a white toner cartridge that contains the white toner contained in the toner set for developing an electrostatic image according to any one of claims 1 to 8 and is detachably attached to an image forming apparatus; a color toner cartridge that contains the color toner contained in the toner set for developing an electrostatic image according to any one of claims 1 to 8 and is detachably attached to an image forming apparatus; Toner cartridge set including:

11. a first developing means containing the white electrostatic image developer included in the electrostatic image developer set according to claim 9; a second developing means containing the color electrostatic image developer included in the electrostatic image developer set according to claim 9; Equipped with A process cartridge that is detachably attached to an image forming apparatus.

12. a first image forming means for forming a white image by using the white toner, the first image forming means comprising a first developing means containing the white electrostatic image developer included in the electrostatic image developer set according to claim 9; a second image forming means for forming a color image by using the color toner, the second image forming means including a second developing means containing the color electrostatic image developer included in the electrostatic image developer set according to claim 9; a transfer means for transferring the white image and the color image onto a surface of a recording medium; a fixing means for fixing the white image and the color image transferred onto the surface of the recording medium; An image forming apparatus comprising:

13. A first image forming step of forming a white image by the white toner contained in the toner set for developing electrostatic images according to any one of claims 1 to 8; A second image forming step of forming a color image by the color toner contained in the toner set for developing an electrostatic image according to any one of claims 1 to 8; a transfer step of transferring the white image and the color image onto a surface of a recording medium; a fixing step of fixing the white image and the color image transferred onto the surface of the recording medium; The image forming method according to claim 1,

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